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Infrastructure for One Million Email Accounts?
cfsmp3 asks: "I have been asked to define the infrastructure for the email system for a huge company, which fed up of Exchange, wants to replace their entire system with something non-Microsoft. I have done this before, but not for anything of this scale. Suppose you are given a chance to build from scratch an email system that has to support around one million accounts. Some corporate, some personal, some free. POP, IMAP, webmail, etc are requirements. The system must scale perfectly, 99.9% uptime is expected... where would you start?"
I'd start by submitting a question to Ask Slashdot.
gmail.google.com
Support the First Amendment. Read at -1
bashing my head up against a desk.
Ooo man the floppy drive is broken. No wait. The computer is just upside down.
I'd start by contacting people who know how to do it and can actually help you. A few responses on slashdot aren't going to help you along the entire process. Maybe even bring in a consultant.
For starters, uptime should usually be higher than 99.9% for this large a site. 99.9% uptime means 40-45 minutes of downtime a month. Try going for 99.99% at least, though this usually increases the cost by about 250% according to what I have seen a few years back.
+1 funny, -2 overrated. Life isn't fair.
A million users and they want POP3? Add a gun and a single bullet to your administration requirements.
At IBM we use Lotus Notes which has saved us LOTS of virus hassles. Every employee has an account and we're something like 320,000 worldwide. The mail "databases" are spread among Domino servers but I don't know what platform these run on, or what hardware specs they have. I imagine it's either Windows or Linux... but who knows, maybe we're using some of our PowerPC-based iSeries servers. These are the boxen formerly known as AS/400.
However, I'd personally ask Google. They've done it and even their search engine has information. I found an interesting link from there detailing the deployment of a large hundred thousand user mail system, from the architecture to the software located on Linux Journal.
I'd start with talking to vendors. Consult with some sendmail gurus, Notes guys, etc. Any of these people/companies would salvate at the thought of being a part of a project this large. First, talk to the client and hammer out the real needs with solid performance requirements, timeframes, growth expectations, (meaning real numbers) etc. Put together a well thought-out Request For Proposal and send them out to as many applicable vendors that interest you. Then just stand back and play the role of ringmaster. The vendors will give you all the ideas you need.
Just do one thing, please: make sure that the client is honest-to-goodness serious about this. I absolutely hate getting pie-in-the-sky RFPs from people who are just kicking the tires. It's a good way to burn bridges by not looking professional.
Entrepreneur : (noun), French for "unemployed"
There are three parts to your system: sending mail, receiving mail, and storing mail. Keep them separate.
Your receivers will be a bank of servers running sendmail. They will do appropriate spam processing to reduce the amount of mail actually received. They feed the data into the storage servers.
The storage system has the data partitioned out so that all the data for one user would go to one server while all the data for another will go to a different one. The storage system also has to provide POP and IMAP access. You may want a special setup where the IMAP or POP service known which server to go to. Investigate having one giant virtual filesystem so that the system isn't too complicated.
Your webmail access will use IMAP to access the actual mail. It can be a completly different system.
The sending system will be a chokepoint for all outgoing mail. You are going to scan it as it goes out to look for virus-sent emails or unauthorized messages. For instance, you may want marketing email to be processed differently than inter-office email and such.
All of these systems will be running sendmail. I know sendmail has a bad rap for being insecure, but the insecurities have been found and since fixed. It is by far the most manageable system when it comes to large-scale deployments with heavy customization.
The radical sect of Islam would either see you dead or "reverted" to Islam.
I agree. The google appliance should implement gmail and a web front end for administration. Like the Colbalt machines of yore, only better. Google-ified.
It really is the best email.
Here's Slidey's post. (Disclaimer: Copyright blahblahblah appropriate people yadda yadda fair use etc etc don't sue me, thank you)
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ok i work for a large uk isp in the messaging (email) operations dept. we currently have 2.5-3 million active accounts (and a load of suspended), and manage anywhere upto 12-16million mails per day
our setup is like this (this is simplistic though):
front line - anti abuse mta's - these do dnsbl type lookups (spamcop, spamhaus and sorbs). we have 9 incoming
next we have mta's. they farm mail off to brightmail servers, which do similar to spamassassin. we have 6 incoming mtas, and 8 brightmail servers (not enough - high load)
after that they farm off to vscans (6)
after that any mail that gets through is delivered to mail stores (8 + 2 hot spares)
what you want to be doing is similar to this above - chaining hte mail from one level to the next. the first level should be the rbl's - these are less processor intensive, and can remove a fair whack of your mails in one swoop. spamassassin is going to be more cpu intensive, since it has to open each mail and read the first x many bytes
id have separate machine(s) holding your master directory, and if you can get directory caches then do that too (to take the load off the master directory) - ours run oracle
i dont know what your budget is, but split up hte different tasks as much as possible. that way if you need to add more to any pool (rbl lookups, spamassassin etc) you just add another machine..
one last thing - we also have a separate box just for postmaster mail (with exim + spamassassin funnily enough) - it tends to get busy
Last edited by Slidey on 09-08-2005 at 11:19 PM
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(end of quote)
I'm not sure that there is any commerical solution that can support 1 million emails well. Hence why Yahoo and Google have built there own custom systems. Some engineering may need to be required.
For pop3 & imap4rev1, look at:
http://www.dbmail.org/index.php?page=overview
Still need an MTA, I think qmail is the fastest, best, but I'd used exim, as its easier.
Database - not sure if MySQL and PostgreSQL will scale with dbmail.
I'd say use FreeBSD, because of the ports collection (Don't linux Flame me). However, something like Solaris 10 x86 (or Solaris+Sun Hardware) might provide a bit better scaling, and HA hardware, SAN support, support in general, etc. Though, a bit tougher on the OSS software installs (In My Experience)
I second that recommendation. I've been running CommuniGate Pro for many years now, and I love it. There's a cellphone provider in sweden that is hosting over a million accounts on a single 8-processor server - but for your requirements I'd probably recommend looking into CommuniGate's clustering solutions.
... I like to keep an open mind, but not so open that my brains fall out. - Judge Harry Stone, Night Court
Gmail is beta.
:)
Gmail does not have guaranteed uptime.
You do not pin your companies communications system on something you cannot sign a SLA agreement with.
need I go on?
1) It'll run on anything - Win32, Linux, BSD, Solaris, x86, XServers, Alphas, Power5
2) It'll scale as big as you can dream - over 5 million accounts with clustering
3) MAPI support
My number one suggestion is hire someone who has built scalable mail systems, and written tons of code to support them: Matt Simerson
You can learn about him, and his mail projects at http://www.tnpi.biz/internet/mail/toaster.shtml
-Chris Knight
-- This sig is only a test. If this were a real sig it would say something witty. --
My slides relevant to this discussion can be found at http://www.shub-internet.org/brad/papers/dihses/ and http://www.shub-internet.org/brad/papers/sistpni/.
And yes, Nick Christenson has been a long-time friend and co-author of mine.
Feel free to contact me directly if you want some referrals.
Brad Knowles
http://daily.daemonnews.org/ -- if you're not
Seriously. If high availability systems is not your company's core competency, call IBM, Red Hat, Sun, Oracle, Novell. Tell them you have a million users. Tell them you have a very fat checkbook and that you want them to provide you with a complete solution. Tell them that nothing but 5 nines of uptime will do.
DO NOT implement a half-assed solution. Unless you really know what you're doing (and if you were, you wouldn't be asking this question), don't assume that a million Linux servers strewn about a million offices and data centers is the best solution, even if it is easiest to set up and administer. Maybe it is, come up with a proposal with hard numbers and see how they compare to the vendors. A million dollars spent on a Sun E10000, and Oracle Grid subscription (scales perfectly, right?), or a million IBM engineers flown into your site when an emergency happens may be worth paying for.
Or outsource the whole damn thing. There are dozens of providers out there that could drop a rack worth of gear into your datacenter and maintain the whole thing with plenty more experience in handling mail systems of that size. And at that level, I'm sure you'd have no problem getting it branded however you like.
disclaimer: I work for one of those companies.
.
(1) Plan an server setup which can handle the load. The requirements may change, but one million users is a fair bit. How much average incoming and outgoing emails is that? Figure that out, using a network sniffer or sniffers on existing traffic if need be (although logs should work). Then use this to calculate a number of servers needed for an outgoing smtp farm, an incoming MX farm. Figure out how much storage space is to be provided per user, and then figure out how you want that storage space to be accessible. Probably your best bet is to have a round-robin DNS farm of imap/pop servers which proxy connections based on the users login to a backend farm of actual mailservers responsible for storage. Plan the ability to move users from server to server to rebalance as needed. Outgoing smtp is a lot easier since you're not really storing things long term. Plan a web farm for webmail. (And pick software) Don't forget to plan some sort of backup, and make sure your system is flexible as far as email retention; chances are the email retention policy will change at some point and your setup should be able to change with it.
. html
(2) Test. For each server, hammer it. Test it's load under as close to real world circumstances as you can. Then create unreal punishing loads and see how it handles it. Plan in advance for how your server farm handles something like virus-generated mass emails causing 1000% spikes in load.
(3) Using your testing results, spec out the actual hardware. RAID, cheap hardware, redundancy, etc. If you have control over the network choice, plan a location with multiple fiber trunks coming into the building and provider redundancy. Remember backhoes in concert? Don't get hit by that. Plan for server failures, drive failures, network failures, power failures, and security compromises.
(4) Deploy! If you did the rest right, this is the easy part. You'll have redundant network connections, HSRP, redundant switches, a proxy farm, an imap/pop farm the proxies connect to, an smtp farm for outgoing emails, and a web server farm for serving up webmail (depending on how you choose to architect the disk space, the web farm and the pop/imap farm may be one and the same; depends on how you set things up.)
Here's a starter link to a setup which is smaller but, in principle, fairly similar:
http://www.itd.umich.edu/umce/features/2004/cyrus
Finally, if you don't want to screw it up, ask someone who has done it before. Paying someone $300/hr for a 10-30 hour review of your plan is dirt cheap compared to horking the setup. Someone who has worked in huge email environments (a la, hotmail) could show you gotchas before they bite you. (If you need help figuring out who to ask, I could even point you to some of the appropriate people)
Gee whiz... I'm surprised that the groupware is getting tossed out. If as small as 20% of the user is accustom to Outlook Calendaring, they'll represent 95% of the complaints in a new system. An advance warning to all existing account should be mailed out (both paper and email) so that nothing falls through the cracks.
Now to the mega-infrastructure that I set up for an undisclosed company for under 50K (and also didn't want groupware).
1. Transport Sender (sendmail). That's right! Good ol' plain sendmail scales. It does require some pretty savvy tweaking so get Sendmail.Com consultant onboard just for this. Use SleepyCat DB for speed for all sendmail setups. For one million, I had about 23,000 transaction per minutes during the day. You'll require 10 servers for this for cushion (against some idiots sending an ISO attachment).
2. Payload receiver (sendmail). A second group of machine to handle the reception of SMTP payloads.
3. IMAP4S/POP3S - Hey what's with the "S"? Nothing like sending your user's password in the clear. Unless you enforce VLAN in your corporate environment and limit all IMAP4/POP3 to VLAN, the "S" is a mandatory security feature, inside and outside. Guess what "S" stands for?
4. Webmail - SquirrelMail - Yet another dedicated server (in which I had to add two more load-balanced server to handling the growing pain). Use https for login only.
5. AntiVirus (ClamAV) - It was the best back then, now its just running in the middle of the pack. sendmail has milter that allows extensibility such as MIMEDeFang, wilter, rureal (reverse-DNS check), spamassasin, and SPF.
6. Support - Half the effort is put into those webpages that would 'hand-hold' these newbies into reconfiguring their machine. Worth the effort if you have over 20 expert PC users that can do their boxens. Otherwise do it yourself at each PCs. These pages should cover Thunderbird, Evolution, as well as Outlook and Outlook Express.
7. Learn to spin 11 plates, one on each pole. Keep them spinning... If they start to drop and break, bring in some more Unix dudes.
This is the best advice he'll get? Sheesh.
Think this through -- a lot of e-mail programs check every 20 minutes. Assuming I actually hit any without duplications, I could potentially need 400 minutes or over six hours to get all my mail. Since it's random, it could take days.
And that's just for starters with this lame scheme. If I want to check mail, say, from the field on a dial-up once a day... hopefully you can see how badly this would suck.
What the guy should do is buy an e-mail system that can handle 1,000,000 users and not screw around trying to chewing gum his own solution.
Sometimes it's best to just let stupid people be stupid.
My job is building systems like this. Current mailserver system I designed and built is hosting 80,000 email accounts, and will scale out to a million quite cheaply by just adding more machines.
/maildirs/domain.com/user/Maildir - split the domains up with a 2 level deep hashing algorithm (if you're virtual hosting domains, which is what it sounds like to me), so make it something like /maildirs/xx/xx/domain.com/user/Maildir, where xx/xx might be something like 3f/6b (depending on the hash). Use MD4 for the hash because its more balanced than MD5.
/var/spool/exim the internal mirrored disks. DHCP them, then all you do is plug a machine in and set it to PXE boot. Pretty trivial to do.
:)
OpenLDAP
You need a central configuration repository to store the email accounts, their passwords, etc. OpenLDAP is perfect for this, and you can replicate it out for scalability. Be prepared to learn about LDAP schemas.
Exim
Use Exim because it has a simple process model (a single binary that does all the work, like sendmail) but has a human readable configuration file and has to be the most flexible MTA out there. You will have customers with weird requirements sometimes, and Exim will be able to meet those. Plus, it has Exiscan-ACL built-in these days, which allows you to do virus scanning and spam scanning at the DATA stage, before the mail is actually accepted by the MTA. It means you can make the sending MTA deal with the bounces if the mail is a virus or is obvious spam.
Courier-IMAP for POP3 and IMAP access.
Yeah its written by a sociopath, but nothing else works as good in the field. It works out of the box with sensible LDAP schemas and is fast, reliable and secure. Handles SSL, all the different authentication methods, what have you. Maildir compatible.
Maildir message store.
Store the mail in maildirs. Don't put them in
NFS mount the maildirs from a fast NFS device like a Netapp. Netapps are recommended because you can plug them in, and they just work, plus they are easy to scale by adding more trays.
Linux NFS servers set up with heartbeat and shared disk also make a nice HA NFS, and would be cost effective, but you'll have to buy an array anyway (probably fiber channel) so it might be better just get something thats completely integrated like the Netapp.
Spamassassin.
Can be configured to scan make at DATA time in the SMTP conversation. A LOT of configuration work here to make it play nice on a massively scaled platform, but it can be done. Mostly it needs to have things like the auto whitelisting and bayseasn filtering turned off, as the extra DB file work is a bit excessive.
Actually, I'm sure there is a way to make it work with a less resource intensive repository, but using the standard SA rules seems to work well for my environment. *shrug*
ClamAV.
Free antivirus, it works, and integrates well with Exiscan-ACL. Set it up to scan via the daemon, and configure it to update every couple of hours from cron, and bob's your uncle.
Scaling out
Make every box the same. Make every box an MTA, a POP3/IMAP server, etc. Use something like Kickstart to automate builds so that you can build a machine in 10 minutes, and all you have to do is configure the IP address and plug it in. If you want to be REALLY sexy, you could make the machines boot off the network, and mount / from a shared NFS area, and make
Load balancing
Hardware load balancers are pretty much a necessity. Don't touch cisco stuff. Its not very good. Go with Foundry Networks ServerIrons. The XLs can handle 1 billion requests/day if you configure them in Direct Server Return mode (also known as DSR/Foundry switchback). Use it. It makes all the return traffic go directly out to the net, meaning your ServerIrons have to switch less traffic and track less sessions. I would recommend however for a million users a pair of the ServerIron 450GTs, or bigger. Maybe one per VIP/Service.
Now, if this is all looking pretty daunting, you could always hire me to build it for you
... Is anyone wondering what's going on at Microsoft right now?
It starts with a slashdot geek working in the email department spitting up his coffee, followed by a few rumors which make it up to a guy in accounting and customer service, followed by frantic management emails, including some inappropriate language, from Steve and Bill. Then a few good geeks start tracing who this cfsmp3 guy is and try to trace him to a company while the salesreps begin coldcalling any customers running around 1 million customers.
And Microsoft will botch it because they have no experience in cowtowing and bootlicking, which are important skills for any company who wants to humbly keep its customers.
"All great wisdom is contained in .signature files"
Don't get me wrong. Notes isn't just a crappy E-mail client. It's also a crappy database access client that provides user-definiable forms which can be used to populate rows in the database. When you start getting a LOT of rows, the performance really goes to shit unless you replicate the database down to your local hard drive.
Rather than the Notes based solution, I would suggest an old 386 running BSD and Sendmail. That'd save you a lot of pain in the long run, versus dealing with Notes.
I'm trying to teach myself to set people on fire with my mind... Is it hot in here?
First, you need to start by drafting real requirements. What do you need exactly? Antispam? Antivirus? Try to have it fill up at least a page.
Once you have that done, you can start looking at solutions. You will have two parts to your solution:
1) The DMZ email relays (possibly including other antispam/antivirus functions) You really need high availability here.
2) Your email storage and retrieval systems. These may be a little more tolerant to downtime on an individual basis. But if you need to have redundancy here, there are ways to do it.
I think Hotmail did fine with BSD and Qmail.* I am sure Postfix is equally capable.
* Although Qmail itself has never had a security vulnerability discovered, you should be careful. TCPRules (on which qmail relies) has a vulnerability that can lead to root access for local users. This is not a problem on systems with no local users, however. I am not aware of any patch for the TCPRules vulnerability.
LedgerSMB: Open source Accounting/ERP
My God no! Friends don't let friends use qmail. Want reasons why?
1) It's a bitch to install. Won't even compile on modern Linux distributions. You have to patch it to compile it and the patch isn't even hosted on qmail's site.
2) It's a bitch to configure. Rather than parsing a single configuration file, qmail relies heavily on the presence of individual files in a directory.
3) Not not not not scalable! That's a myth. Doesn't properly batch jobs together. Hell! qmail was originally designed to be run from inetd!
4) Heavy reliance on other daemontools.
5) Breaks well-known and understood UNIX standards.
6) Security through lack-of-functionality.
7) Not really secure despite the claims.
8) No longer maintained.
9) No features. Adding them requires patching, and patching, and more patching.
Serious sysadmins don't use qmail and for damn good reason. I don't give a damn if Yahoo did manage to string it together and make it work well. In short, qmail isn't particularly suited for deployment in any capacity.
Slackware, what else when it must be secure, stable, and easy?
Resign. You're obviously in way over your head if you have to resort to asking Slashdot readers for advice like this.
Hi Cliff;
:)
;)
Sounds like a fantastic design opportunity here. The 5% of the project that is Enterprise architecture is what I enjoy the most as well. I'm assuming money probably isn't an object in terms of how much gear and bandwidth you may have to feed to this.
I'm happy to let my fingers type away below, I'd love to keep in touch and see how you end up shaping this system. my email is allowmx at hotm...
Before I ask, are there actually a million accounts? Or is that just a ceiling that you have to show proof of concept with?
I've only implemented up until about 250,000 accounts of any kind, as I'm sure you're probably aware, the base transactional resource costing is essentially the same..
For me, I would look at this for sure from at least these two angles:
1) knowing your transactional costs (how much of your hard resources, bandwidth, cpu and disk space) will each type of transaction in your system take?) I mostly use this approach to get not an exact number, but an idea of magnitude, and detail where it happens on it's own to make sure the proper attention is applied to them.
2) Failsafe intelligence & capacity in the infrastructure, as well as the failsafe intelligence & capacity in at the application layer. You have to know that your hardware, software, os, business logic and applications are all monitorable internally, externally for availabilty and actual "can I use it". Transactional logs, etc, of having information available when the inevitable problems come up.
Also, having a capacity for as many of these layers to be self-healing, and fungible to the point that your service delivery is homogenous in as many ways possible. If your network finds something doesnt work or route, with mail, you can find another way to route it. Having a transactional manager of some kind, direct or not, could be useful in this case depending on what the client wants.
99.9% uptime equates to about 526 minutes, or 87.6 hours you _could_ be down each year. Thats about 7.3 hours a month, or one day a month.
Based on that, having flexible, redundant tools setup in a high-availabily arrangement at their respective operating capacities is key. I'm not sure if your current exchange problems are being aided by not enough equipment, bandwidth, or other stability issues, so I'll just assume that it's all of them
I apologize if anyone else has already mentioned some of this, but here's some of what I've found to help me where email has become as crucial to a business as their cell phone.
On the hardware level:
- STORAGE: Everything goes on a SAN, if not more than one. Don't waste your time with anything less.
- SERVERS: All servers have redundant hot swappable parts in the very least, power and hard drives. I'd even suggest making the servers Iscsi bootable so they can boot off the backbone. Beyond this, I like to buy my servers in piles of identical ones. Have 1-2 spare serevrs of each kind sitting there, ready to throw hot swap drives into from a failed server. That way if a server dies, you can address the power supplies, or get the HD's in that machine into another identical server and get it up and running while you diagnose the hardware problem independantly. My approach to any kind of problem is FIX, DETECT and REPAIR. Get it up and running, find out what was wrong, make sure it's fixed for good. Too many of us stop at the first too
The idea I have in mind is a smaller scale of a google beige box army. linux/bsd offer so much more transcations for each piece of hardware, so that works very much in your favor. Obviously something enterprise grade to satisfy the client such as the Compaq/HP Proliants, etc. I feel these Servers ahve the best overall support, manageability and information tools, and their openlinux drivers interface wonderfully with open source operating systems)
Networking/Communication level:
- Entire mail processing architechture communi
Of course, everyone should note that recommendation is coming from an IBM employee.
Sorry, but Lotus Notes sucks; it's an abomination in almost every way. It's bloated, slow, buggy and has what is arguably the worst user interface ever (The User Interface Hall Of Shame said they could have based their entire site on this one app!) Sure, it does group meeting notes and can let you check other people's calendars but it falls flat as an email system. If it can't do the basics, who cares about the "advanced" features.
Doubt me? Okay. Let's try a little experiement.
First, sort your inbox by subject. Oh, I forgot. YOU CAN'T. Well, let me take that back. You can if you simply follow these simple instructions...
First, you need to have Domino Designer installed. In Designer, open Folders in left pane, then open folder $Inbox, highligh the Subject column. In the window with Columns properties in second tab you can check-in the "Click on column header to sort..." checkbox. Close $Inbox folder window. To prevent design refresh, in Folders view, right-click on $Inbox folder, choose Design properties and on third tab check-in "Prohibit design refresh or replace to change".
[blinks eyes in disbelief]
Un. Fucking. Believable.
Oh, and the feature I like the best is the pop-up dialog that tells you you have new mail. So you click to make that go away, switch over to LN to read the new mail and it's not there... Oh, yes, that's right, you have to press F9 to actually download the email to your client, even after being notified by an obnoxious popup that you have new mail.
Want to know another neat little feature related to that F9 key? According to our LN System Admin, get a few dozen people to all press and hold the F9 key for a few seconds at the same time and you can crash the Domino server backend requiring the server to reboot. Nice.
I could go on but I think I've made my point. I have never, ever, encountered anyone who has switched from Notes and been pleased with the change.
A single server? For one million users?
Insert "imagine a beowolf of those" joke here, except it isn't a joke.
I think you might be underestimating the requirements for this large a project that "must scale perfectly". The "99.9% uptime is expected" requirement alone requires multiple internet connections, a large cluster of front end servers, and redundent database servers, preferably located in different states. (ie: "What do you mean our only server is in New Orleans?")
I don't think the average Dell dual Xeon box is up to the task for this large a project...
Tequila: It's not just for breakfast anymore!
Definately agree on point 9. I maintain a mail server of over 2,000 users. Currently running Qmail with the following patches:
chkuser-2.0.8b-release.tar.gz
doublebounce-trim.patch
netqmail-1.05-tls-20050329.patch
outgoingip.patch
qmail-smtpd-auth-0.31.tar.gz
qmail-smtpd-auth-close3.patch
qmail-smtpd_gmfcheck.patch
qmail-spf-rc5.patch
Most of these patches require hand editing the sources and Makefiles to successfuly merge them all into the stock qmail or netqmail base. Lots of manually reading through *.rej files to make it all work.
In order to simplify new installations I've created my own personal CVS repository for my Qmail sources. I commit changes to the tree whenever a new patch comes out with functionality I need. Hence on a new install I simply check out my custom tree and compile.
The initial work was a royal pain in the ass, however, once it is all up and running the stability and performance has been excellent.
While not quite a million users, HEC Montréal switched from Netscape Messaging Server running on AIX to Postfix/Cyrus/SquirrelMail running on Linux. Linux Journal ran a really nice article and a follow-up about their transition.
One of the first things the school did was figure out how exactly their current system was failing them. Their old AIX boxes were being stressed just by the volume of mail coming through the system, they had little power left over to do any sort of filtering. This led to users getting drowned in unwanted e-mail which only exacerbated the existing load issues. This is one of the first things you need to do, figure out why your current system isn't working properly. You'll be better equipped to fix the problems when they've actually been identified.
HEC Montréal also went for heavy redundancy and specialization. Instead of a handful of servers sharing all of the tasks equally each node in the cluster has its own job with every class of job having a backup server. Every job is going to take a beating with so many users, even if only a fraction of them are using the system at any given time.
I'd say the most important part of what you're doing will be modeling your current use. Are you getting a ton of traffic from viruses and worms spreading over your internal network? Do you get huge amounts of spam traffic to users? In such cases filtering at your SMTP servers will relieve the rest of the system from extraneous traffic. While you might need really beefy external SMTP servers you won't need nearly as much storage space on a SAN or NAS.
I'm a loner Dottie, a Rebel.
AKO (www.us.army.mil) is the Army's official intranet portal. We provide email for over 1.72M users, and we move almost 3 million messages a day. We do it all with Sun Messaging Server ver5.2 (soon to be Jes3) and we have exactly 2 (count 'em) two mail administrators. Sun mail is rock solid and scales great. We offer POP, SMTP, enterprise SPAM and Virus filtering as well as personal address books besides. We don't get the rich Outlook fat client, but then we want to be all web-based anyway. Can't say enough about Sun mail. If we had to do this with Exchange, I'd have to hire prolly 50 admins and deploy order of magnitude more machines.
No. 0.1% != 0.1
365 days * 24 hrs/day = 8760 hours per year
0.1% downtime = 0.001 downtime
8760 * 0.001 = 8.76 hrs
You're off by two orders of magnitude.
8.76 hrs / 12 months = 0.73 hrs/month = 43.8 minutes/month
One 45 minute scheduled downtime (assuming its scheduled) per month isnt terrible. It's not great, but costs really start to go up as you add nines beyond those 3.
Want a high quality FOSS RTS game? Try Warzone 2100!
There is absolutely no reason at all to leave 80% free space, 15% is more than enough to ensure you don't have fragmentation problems (I am assuming you are using a reasonable filesystem of course).
Second, people with rediculously frequent mail check times are not any more of a problem. Modern operating systems use file system caches. You do not have to touch the disk subsystem in any way, frequently accessed data will be in RAM.
And finally, a database has alot of extra overhead, and there is alot of deletes going on. Sure, such a select statement would work, but reading the files in one directory is an order of magnitude faster. And the deletes will really hammer your database. FFS+softupdates makes file deletion extremely fast. A relational database is not the answer for everything, stop trying to pretend it is. Use the right tool for the job, and for storing files, a filesystem is the right tool. Its not relational data, it doesn't need to be queried in arbitrary, complex ways, so it doesn't belong in a relational database.
Yeah. Well, if 1 minute, 26 seconds is "almost" 15 minutes, anyway.
I read Usenet for the articles.
All of these systems will be running sendmail.
You're high. Building a massive production email system on Sendmail 9 is slow-motion suicide. If the security holes don't get you, the terrible configuration methods and complete lack of scaleability will, nevermind the fact that Sendmail Inc is trying desperately to replace the product.
"Most managable with [...] heavy customization?" I'd laugh if I wasn't crying. And I'm crying because I used to work for a company that deployed a massively customized sendmail infrastructure -- and I was one of the poor bastards who had to maintain it. Trust me, you don't want to do this. Ever.
Yes, milter is cool. No, it's not cool enough to justify burning CPU cycles on sendmail in 2005.
Even Sendmail Inc tacitly admits that Sendmail's design is garbage: take a look at the design document for Sendmail X, and note carefully how much it resembles Postfix and Qmail. There are very good reasons for this.
News for Nerds. Stuff that Matters? Like hell.
You used to work for NASA right?
From ASR ( http://home.xnet.com/~raven/Sysadmin/ASR.Quotes.ht ml )
... while talking to bloat.example.com.:
Re : Mail Transfer Agents
Qmail : a small office of neatly dressed clerks, delivering short clipped remarks to queries, and handling mail with a rude impersonality, except in the case of failiure where they let their hair down and have an after-hours beer and let you know about it, pointing to the pertinent header sections.
MMDF: A jumped up mailroom boy with a chip on his shoulder. Loves the bureaucracy and takes great pride in stamping "illegal address" in red ink on any mail it passes. Unpacks all the mail and repacks it in his own special envelopes before delivery to end users.
PP: MMDF gone mad with standards fever. Think "Brazil".
No, PP is... well, see, when it receives a letter, it chops it into small pieces, then translates bits of it using an English-Hungarian phrasebook and puts all the bits into various pigeon-holes. When it gets round to delivering the message, it collects all the bits, translates them back using a Hungarian-English phrasebook, tapes them together, and loses the letter. Some time later, you get a bounce message:
----- The following addresses had permanent fatal errors -----
----- Transcript of session follows -----
>>> RCPT To:
550 My hovercraft is full of eels
PP is John Cleese.
Sendmail: Shiva as a postman. Many arms delivering mail, dancing, taking drugs, destroying as it sees fit. Often makes creative changes to the mail for kicks, but ultimately can be persuaded to do anything with the right incantation...and that includes giving you other people's mail.
VMail: No experience yet, but I'd guess something like a wisened old man sitting on the porch outside the postoffice. Looks at everyone who passes by with deep suspicion, but turns out to be friendly and helpful once he realises you're not there to rob the place.
Micro$oft IMC: The Scarlet Pimpernel of postmen. Hard to find, impossible to order about, but every once in a while it saves a piece of mail from disaster. Sometimes even with it's head(ers) intact.
cc:Mail SMTPLINK: A 5 year old child left in charge of a large sorting office. Can't reach over the counter properly, can't handle more than one letter at once and has to go looking for a grownup whenever it wants to deliver to mail to other towns. Often opens parcels to look for shiney things inside then just delivers the wrapping paper onwards.
cc:mail UUCPLINK: an insane madman sitting in a box. Mail is thrown into a box where unknown things happen to it.. sometimes mail actually leaves the box.. usually to be delivered to the administrator of a totally unrelated postoffice and containing a complaint that the madman could not find the recipient in his dark box and would you please contact the person with the key of the box. Of course, the only way to reach that person is by mail and even if the box is opened the madman cannot be pursuaded to actually send mail to unknown addressees to the person with the key anyway...
Gus, Pete Bentley, Malcolm Ray, Perry Rovers
Backups.
With POP3, the client downloads mail and deletes it off the server. Without a significantly butchered POP3 server there's no way to hold copies of that mail for a period of time (say, to ensure it goes on to your archival tapes, or to make sure you can recover files the user deleted accidentally). It's one less thing to worry about if their workstation / laptop dies, too - just give 'em another one. If more mail clients supported LDAP address books and WebDAV calendars this would be even nicer; as it is I still have to keep their mail folders in their network home dir so I can back up their address book.
You can back up POP3 boxes if you're on a corporate network, by forcing the client to keep its spools on the user's homedir. That tends to be slow and inefficient, though, and it doesn't let you do things like transparently split out attachments and store only one copy of an identical attachment for everybody.
It's also easy to lose mail with POP3 if your client does something silly. Most clients seem pretty decent now, but I remember old Eudora versions used to DELE mail off the server then crash, corrupting their mailboxes. Woohoo.
IMAP gives admins much more control over user mail. You can back up their mail folders, including their outbox and filed mail. You can enforce mail lifetime limits if your information retention policy requires it. You can store single copies of duplicate messages and attachments. You can give users access to shared mailboxes, and to each other's mailboxes where necessary. You can manage their mail folders remotely ("I can't delete $message, help!"). You can set up filters that deliver mail into sub-mailboxes automatically. Good clients automatically sync the IMAP mailbox so it can be used when the client is offline, like POP3. You can have your anti-spam software learn from their mail client's Junk folder. It's just much saner for business environments, in much the same way that network home directories and thin clients are much saner than a bunch of desktops with local storage are.
IMAP also permits you to give the user a single view of their mailboxes from their desktop and when they're on the road, or accessing their mail from home. Don't even talk about "leave mail on server" for POP3 - users WILL misconfigure it and suck all their mail down onto one of their machines, then come to you looking for help cleaning up the resulting awful mess.
Now, for an ISP, things are the opposite. You want to get the users' mail through your system and get rid of it. Most ISPs only offer POP3 and have small mailbox caps, so the user can't set their client to never delete mail off the server. They don't want to be responsible for user mail, they want it off their hands ASAP. An ISP can just tell a user who deleted a message then wants it back "well, that was silly then wasn't it?". An ISP doesn't want to back up 5 years worth of mail for 500,000 users.
My point is that for corporate environments IMAP is so superior that it's almost nuts to offer anything else, but for an ISP POP3 is a much more viable option. So what's so bad about POP3 depends entirely on what your needs are.
my recommendations:
- Calculate with about 20-30 man days for the initial design. You'll need some software
development for about 30-50 man days, 100 man
days for setup, testing and fine tuning.
Figures may wary upon skill and LWF. Time
for integration into your backup service is
not included.
- Use a directory service with replication mechanism (preferred LDAP, we've done it with MySQL too). Every system except the load balancers will
get a replica.
- The user data is stored on machines with Cyrus . Depending on machine size, user profile, mbox size etc. you take between 5.000 and 50.000 users per system.
- The directory service knows which user is on which system. Prepare a script to move users from
one server to another (including the mbox).
- Incoming IMAP connects go through a loadbalancer to frontend systems with the perdition proxy. Those will relay thre requests
according to the directory to the responsible
IMAP server.
- Incoming HTTP requests will go through the
loadbalance to an Apache with Squirrel on the
frontend systems. Those will convert the requests
into IMAP requests and connect to the local
perdition.
- Generate a web frontend for the user to setup
auto reply, vacation and anti-spam settings.
- From those settings you can create SIEVE scripts for the user.
- Incoming and outgoing SMTP traffic is handled by systems with sendmail. Local delivery is handled by LMTP connects directly to the IMAP servers (cyrus can handle LMTP).
- Antivirus and Antispam is handled through the milter interface and appropiate plugins. Plan for individual settings per user (can be generated
from the data in the directory server).
- Loadbalancing SMTP us trivial.
- Add monitoring (e.g. Nagios), Backup and Restore (last one most important, nobody wants backup, all everyone wants is restore).
- If desired, use a cluster file system for those
IMAP servers to have even more redundancy.
- Make sure you have access to the internal DNS of your company. If you can setup "mail.acmecompany.com" to point to several ips (depending on location) this may ease your job
lot. If you cannot, this may be hard (and expensive) for your load balancers.
- You can scale everything horizontal in this concept. Choking point may be the load balancers.
- You can distribute the system easily onto several locations. Distribution over several continents is only recommended if you can either manage the DNS or the mail agent settings per continent.
Please forgive me, if i'm not completely correct. I'm only the sales repWith backup support you should be able to setup such a system in 6 to 12 months (the later more realistic for big companies).
Most probably users will complain about the lacking calendar.
Most troublesome will be the migration phase (hope you realized i didn't mention it above). This depends so much on your current scenario that it is very difficult to give a general advice.
> where would you start?
Contacting me ;-). Perhaps get a budget first. As i said, i'm sales....
Regards, Martin
What you have here is an opportunity for a tremendous open source win against exchange, and you are about to stuff it up because you do not have a clue how to do it.
So, what you do right now is you go find someone who does know how to do it. And by that I mean someone who can demonstrate they know how. Which does not equate to having a low slashdot id; it equates to having done real projects of this scale.
So, how do you start? You ring IBM and get them to come in and talk to you. You ring Red Hat. You ring Accenture.
If you want impartial advice from someone who isn't a vendor (which is a good idea), then you go find some companies that has a million seat open source e-mail deployment in place and you see if you can get their messaging admin to talk to you.
~~~~~ BigLig2? You mean there's another one of me?
When it works at all it's slow. Sometimes you can hit the Send button and just sit there and wait a while.
When we have to work on a Navy project we had to start bringing our own equipment and hubs. Even their developer machines come loaded with 10 year old software and you can't get your email and be logged in as a developer at the same time. To check mail you have to log out, log back in under a different account, then log back in as a developer. The NMCI machines are boat anchors.
NMCI is the worst defeat the US Navy has ever suffered.
That's our life, the big wheel of shit. - The Fat Man, Blue Tango Salvage
In my opinion you're going to need a cluster of servers or at least round robin'd mx records for the servers. I personally think sendmail scales the best of the mta packages and offers the best set of features and ease of maintenance, although alot of people would argue it's intrinsicly insecure... I've never had problems, but I kept our mail servers up to date. I would seperate the smtp machines the outside world uses to deliver mail to your space from the servers used by users of your service to deliver mail. I would also move delivery services (imap, pop, webmail) to their own machines instead of having them on the smtp machine and you would probally be best to use a nas for the actual storage medium. This is actually a really interesting project. Good luck and let us know how it turns out :)
Shadus
Of course nearly everyone who uses it hates it, because it seems unnecessarily complicated. But this is precisely the kind of situation Domino was designed to handle: scaling. If you can get by with Sendmail, you don't need or want Domino, but if you want to manage a million email accounts, this is one of the first places I'd look.
This is exactly what Notes was designed to do: scale. People have been building systems on this scale with notes for nearly twenty years. You can not only scale it by moving parts of your email system onto mainframe class iron, but you can distribute it and provide all kinds of flexibility and redundancy into your system to meet virtually any messaging requirement (e.g. choose an alternate MTA for high priority traffic when there are Internet disruptions). Naturally there's some complexity involved, but if you can get by with sendmail you probably shouldn't be using Notes.
What's more important is that management of accounts and identity, which is distributed, delegatable, and backed up by robust cryptographic certificate management. You can let a subsidiary manage it's own accounts, they can subdelegate that to a division and the division can subdelegate that to the IT staff on site; at each level policies can be set, enforced, and changed for lower levels.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.