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Ask Slashdot: Best *nix Distro For a Dynamic File Server?
An anonymous reader (citing "silly workplace security policies") writes "I'm in charge of developing for my workplace a particular sort of 'dynamic' file server for handling scientific data. We have all the hardware in place, but can't figure out what *nix distro would work best. Can the great minds at Slashdot pool their resources and divine an answer? Some background: We have sensor units scattered across a couple square miles of undeveloped land, which each collect ~500 gigs of data per 24h. When these drives come back from the field each day, they'll be plugged into a server featuring a dozen removable drive sleds. We need to present the contents of these drives as one unified tree (shared out via Samba), and the best way to go about that appears to be a unioning file system. There's also requirement that the server has to boot in 30 seconds or less off a mechanical hard drive. We've been looking around, but are having trouble finding info for this seemingly simple situation. Can we get FreeNAS to do this? Do we try Greyhole? Is there a distro that can run unionfs/aufs/mhddfs out-of-the-box without messing with manual recompiling? Why is documentation for *nix always so bad?""
Why do you need a unified filesystem. Can't you just share /myShareOnTheServer and then mount each disk to a subfolder in /myShareOnTheServer (such as /myShareOnTheServer/disk1).
I know I’m not going to be the first person to ask this, but if I understand it the plan here was:
1 - buy lots of hardware and install
2 - think about what kind of software it will run and how it will be used
I think you got your methodology swapped around man!
Why is documentation for *nix always so bad?
You are looking for information that your average user won’t care about. Things like boot time don’t get documented because your average user isn’t going to have some arbitrary requirement to have their _file server_ boot in 30 seconds. That’s a very weird use case. Normally you reboot a file server infrequently (unless you want to be swapping disks out constantly..). I’m assuming this requirement is because you plan on doing a full shutdown to insert your drives... in which case you really should be looking into hotswap
Also mandatory: you sound horribly underqualified for the job you are doing. Fess up before you waste even more (I assume grant) money and bring in someone that knows what the hell they are doing.
Why does it have to be a mechanical hard drive? Why not use an SSD for the boot drive?
Really, singular hard drives are notoriously bad at keeping data around for long. I would make sure you have a copy of everything. So make a file server with RAIDZ2 or RAID6 and script the copying of these hard drives onto a system that has redundancy and is backed up as well.
How many times I have seen scientist come out with their 500GB portable hard drives and they are unreadable... way too much. If you fill 500GB in 24 hours, there is no way a portable hard drive will survive for longer than about a year. Most of our drives (500GB 2.5" portable drives) last a few months, once they have processed about 6TB of data full-time they are pretty much guaranteed to fail.
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Scientific Linux is also a good option for similar reasons. Given its a science grant, they might like the idea that its used at labs like CERN
Another "I don't know how to do my job, but will slag off OSS knowing someone will tell me what to do. Then I can claim to be l337 at work by pretending to know how to do my job".
It's call reverse physiology, don't fall for it! Maybe shitdot will go back to its roots if no one comments in junk like this and the slashvertisments?
Not sure why the 30s boot up requirement is there, so it depends on what you define as "booted" . Spinning up 12 hard drives and making them available through Samba within 30s guarantees your costs will be 10x more than they need to be.
This isn't another example of my tax dollars at work is it?
Why would you want a file server to boot in 30 secs or less? Ok, lets skip the fs check, the controller checks, the driver checks, hell lets skip everything and boot to a recovery bash shell. Why would you not network these collection devices if they are all within a couple of miles and dump to an always on server?
I really fail to see the advantage of a file server booting in under 30 seconds. Shouldn't you be able to hot swap drives?
This really sounds like a bunch of kids trying to play server admin. My apologies if this is not the case, but given the parameters provided this IS what it sounds like.
"Enterprise class" is a marketing slogan. In the real world, all the RH derivatives are pretty good (including Scientific Linux and Fedora as well as CentOS), and all the Debian derivatives are pretty good (including Ubuntu). Gentoo's solid too. "Enterprise class" doesn't mean much. The main thing that characterizes CentOS from Scientific Linux - which is also just a recompile of the RHEL code - is that the CentOS devs have "enterprise class" attitude. Meanwhile, RH's own devs are universally decent, humble people. Those who do less often thing more of themselves.
For a great many uses, Debian's going to be easiest. But it depends on just what you need to run on it, as different distros do better with different packages, short of compiling from source yourself. No idea what the best solution is for the task here, but "CentOS" isn't by itself much of an answer.
"with their freedom lost all virtue lose" - Milton
You know, I was on the "it doesn't matter" camp untill I readed your post. Now I just changed my mind.
Yes, any distro will do it. You'll have the same (lack of) trouble configuring the service on any distro. So, choose a distro that is easy to get into bare bones and to upgrade, because those are the two main differentiators here.
I sugest Slackware. Probably somebody else knows about somethig simpler, but not so simple that it will end up giving you more work.
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Booting in under 30 seconds is going to be a bit of a trick for anything servery. Even just putzing around in the BIOS can eat up most of that time(potentially some minutes if there is a lot of memory being self-tested, or if the system has a bunch of hairy option ROMs, as the SCSI/SAS/RAID-generally disk controllers commonly found in servers generally do...) If you really want fast, you just need to suck it up and get hot-swappable storage: even SATA supports that(well, some chipsets do, your mileage may vary, talk to your vendor and kidnap the vendor's children to ensure you get a straight answer, no warranty express or implied, etc.) and SAS damn well better, and supports SATA drives. That way, it doesn't matter how long the server takes to boot, you can just swap the disks in and either leave it running or set the BIOS wakeup schedule to have it start booting ten minutes before you expect to need it.
Slightly classier would be using /dev/disk/by-label or by-UUID to assign a unique mountpoint for every drive sled that might come in from the field(ie. allowing you to easily tell which field unit the drive came from).
If the files from each site are assured to have unique names, you could present them in a single mount directory with unionFS; but you probably don't want to find out what happens if every site spits out identically named FOO.log files, and(unless there is a painfully crippled tool somewhere else in the chain) having a directory per mountpoint shouldn't be terribly serious business.
500G in a 24h period sounds like it will be highly compressible data. I would recommend FreeBSD or Ubuntu with ZFS Native Stable installed. ZFS will allow you to create a very nice tree with each folder set to a custom compression level if necessary. (Don't use dedup) You can put one SSD in as a cache drive to accelerate the shared folders speed. I imagine there would be an issue with restoring the data to magnetic while people are trying to read off the SMB share. An SSD cache or SSD ZIL drive for ZFS can help a lot with that.
Some nagging questions though.
How long are you intending on storing this data? How many sensors are collecting data? Because even with 12 drive bay slots, assuming cheap SATA of 3TB a piece. (36TB total storage with no redundancy), lets say 5 sensors, thats 2.5TB a day data collection, and assuming good compression of 3x, 833GB a day. You will fill up that storage in just 43 days.
I think this project needs to be re-thought. Either you need a much bigger storage array, or data needs to be discarded very quickly. If the data will be discarded quickly, then you really need to think about more disk arrays so you can use ZFS to partition the data in such a way that each SMB share can be on its own set of drives so as to not head thrash and interfere with someone else who is "discarding" or reading data.
"Enterprise class" means that it runs the multi-million dollar crappy closed source software you bought to run on it without the vendor bugging out when you submit a support ticket.
Unless you're talking about millions of individual files on each drive it should be relatively quick to mount each hard drive and set up symbolic links in one shared directory to the files on each of the mounted drives. Just make sure Samba has "follow symlinks" set to yes and the Windows clients will see just see normal files in the shared directory.
Why is documentation for *nix always so bad?""
For starters, I'm really tired of this /. *NIX is-too-hard ranting all the time on 'Ask Slashdot' posts. Don't be a n00b douche; if you don't get it, then spend some time and get it. Don't blame the documentation; dig in and figure out something for yourself for once. Sometimes you Nintendo-and-Mt-Dew generation make me want to throw up.
As for your solution, do-not go with some installable appliance-type distro like FreeNAS; yes it's *BSD under the hood, but you're at the mercy of what that 'focused' distro is goign to provide for you. Case in point: since you're undecided, go with a full-blown distro so you have some flexibility to grow and augment the mission and purpose of this server you're hosting data on.
Since you're clearly a n00b since it's coming to picking out a *NIX solution, go with anything Linux at this point, and set up the NAS services yourself (e.g. Samba/SMB, NFS, etc.) In turn, you'll be able to go to get better community support helping you out, you'll have more flexible OS configuration and growth, and you'll probably learn something to boot.
Also, you don't need to do union filesystem. Simple udev rules and auto mounting them under your top-level structure you're sharing out with your NAS services will do you just fine.
What is the point of 30 second boot on a file server? If this is on the list of 'requirements', then the 'plan' is 1/4 baked. 1/2 baked for buying hardware without a plan, then 1/2 again for not having a clue.
unioning filesystem? what is the use scenario? how about automounting the drives on hot-plug and sharing the /mnt directory?
Now, 500GB/day in 12 drive sleds....so 6TB a day? do the workers get a fresh drive each day or is the data only available for a few hours before it gets sent back out or are they rotated? I suspect that mounting these drives for sharing really isnt what is necessary, more like pull contents to 'local' storage. Then, why talk about unioning at all, just put the contents of each drive in a separate folder.
Is the data 100% new each day? Are you really storing 6TB a day from a sensor network? 120TB+ a month?
Are you really transporting 500GB of data by hand to local storage and expecting the disks to last? reading or writing 500GB isn't a problem, but constant power cycling and then physically moving/shaking the drives around each day to transport is going to put the MTBF of these drives in months not years.
dumb
Saying "only good mp3 player" makes no sense unless you specify your criteria. Amarok, Banshee, VLC, Rhythmbox, or smplayer are all capable mp3 players by various criteria and easily found by googling for "linux mp3 player". If you use Ubuntu, searching for mp3 player in Software Center finds a plethora of good players. Googling "list of linux audio software" easily finds other things besides just mp3 players: maybe something like Audacity satisfies your requirements better. Search for "mp3" on xmms2.org finds the answer in the first link - your xmms2 install needs have the MAD library, maybe your distro does not install that.
Does not seem like the problem is with bad docs.
"When I first heard Daydream Nation it quite frankly scared the living shit out of me." -- Matthew Stearns
Ok, lots of folks asking similar questions. In order to keep the submission word count down I left out a lot of info. I *thought* most of it would be obvious, but I guess not.
Notes, in no particular order:
- The server was sourced from a now-defunct project with similar setup. It's a custom box with non-normal design. We don't have authorization to buy more hardware. That's not a big deal because what we have already *should* be perfectly fine.
- People keep harping on the 30 seconds thing.
The system is already configured to spin up all the drives simultaneously (yes the PSU can handle that) and get through the bios all in a few seconds. I *know* you can configure most any distro to be fast, the question is how much fuss it takes to get it that way. Honestly I threw that in there as an aside, not thinking this would blow up into some huge debate. All I'm looking for are pointers along the lines of "yeah distro FOO is bloated by default, but it's not as bad as it looks because you can just use the BAR utility to turn most of that off". We have a handful of systems running winXP and linux already that boot in under 30, this isn't a big deal.
- The drives in question have a nearly identical directory structure but with globally-unique file names. We want to merge the trees because it's easier for people to deal with than dozens of identical trees. There are plenty of packages that can do this, I'm looking for a distro where I can set it up with minimal fuss (ie: apt-get or equivalent, as opposed to manual code editing and recompiling).
- The share doesn't have to be samba, it just needs to be easily accessible from windows/macs without installing extra software on them.
- No, I'm not an idiot or derpy student. I'm a sysadmin with 20 years experience (I'm aware that doesn't necessarily prove anything). I'm leaving out a lot of detail because most of it is stupid office bureaucracy and politics I can't do anything about. I'm not one of those people who intentionally makes things more complicated than they need to be as some form of job security. I believe in doing things the "right" way so those who come after me have a chance at keeping the system running. I'm trying to stick to standards when possible, as opposed to creating a monster involving homegrown shell scripts.
You have to be able to identify the disks being mounted. Since these are hot swappable, they will not be automatically identifiable.
Also note, not all disks spin up at the same speed. Disks made for desktops are not reliable either - though they tend to spin up faster. Server disks might take 5 seconds before they are failed. You also seem to have forgotten that even with all disks spun up, each must be read (one at a time) for them to be mounted.
Hot swap disks are not something automatically mounted unless they are known ahead of time - which means they have to have suitable identification.
UnionFS is not what you want. That isn't what it was designed for. Unionfs only has one drive that can be written to - the top one in the list. Operations on the other disks force it to copy it to the top disk for any modifications. Deletes don't happen to any but the top disk.
Some of what you discribe is called an HSM (hierarchical storage management), and requires a multi-level archive where some volumes may be on line, others off line, yet others in between. Boots are NOT fast, mostly due to the need to validate the archive first.
Back to the unreliability of things - if even one disk has a problem, your union filesystem will freeze - and not nicely either. The first access to a file that is inaccessable will cause a lock on the directory. That lock will lock all users out of that directory (they go into an infinite wait). Eventually, the locks accumulate to include the parent directory... which then locks all leaf directories under it. This propagates to the top level when the entire system freezes - along with all the clients. This freezing nature is one of the things that a HSM handles MUCH better. A detected media error causes the access to abort, and that releases the associated locks. If the union filesystem detects the error, then the entire filesystem goes down the tubes, not just one file on one disk.
Another problem is going to be processing the data - I/O rates are not good going through a union filesystem yet. Even though UnionFS is pretty good at it, expect the I/O rate to be 10% to 20% less than maximum. Now client I/O has to go through a network connection, so that may make it bearable. But trying to process multiple 300 GB data sets in one day is not likely to happen.
Another issue you have ignored is the original format of the data. You imply that the filesystem on the server will just "mount the disk" and use the filesystem as created/used by the sensor. This is not likely to happen - trying to do so invites multiple failures; it also means no users of the filesystem while it is getting mounted. You would do better to have a server disk farm that you copy the data to before processing. That way you get to handle the failures without affecting anyone that may be processing data, AND you don't have to stop everyone working just to reboot. You will also find that local copy rates will be more than double what the servers client systems can read anyway.
As others have mentioned, using gluster file system to accumulate the data allows multiple systems to contribute to the global, uniform, filesystem - but it does not allow for plugging in/out disks with predefined formats. It has a very high data throughput though (due to the distributed nature of the filesystem), and would allow many systems to be copying data into the filesystem without interference.
As for experience - I've managed filesystems with up to about 400TB in the past. Errors are NOT fun as they can take several days to recover from.
then get OpenBSD.
If you want different removeable disks to be mounted in different places, it's even easier. Just list each disk (identified by UUID) in /etc/fstab, with the proper mountpoint and include auto in the options. That way, when you plug it in, the system knows exactly where it goes.
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What you're describing sounds like a fairly typical Sensor Net (or Sensor Web) to me, maybe with a little more data logged than is normal per platform. (I believe they call it a 'mote' in that community).
Some of the newer sensor nets use a forwarding mesh wireless system, so that you relay the data to a highly reduced number of collection points -- which might keep you from having to deal with the collection of the hard drives each night (maybe swap out a multi-TB RAID at each collection point each night instead).
I'm not 100% sure of what the correct forum is for discussion of sensor/platform design. I know they have presentations in the ESSI (Earth and Space Science Informatics) focus group of the AGU (American Geophysical Union). Many of the members of ESIPfed (Federation of Earth Science Information Partners) probably have experience in these issues, but it's more about discussing managing the data after it comes out of the field.
On the off chance that someone's already written software to do 90% of what you're looking for, I'd try contacting the folks from the Software Reuse Working Group of the Earth Science Data System community.
You might also try looking through past projects funded through NASA AISR (Adanced Information Systems Research) ... they funded better sensor design & data distribution systems. (unfortunately, they haven't been funded for a few years ... and I'm having problems accessing their website right now). Or I might be confusing it with the similar AIST (Adanced Information Systems Technology), which tends more towards hardware vs. software. ... so, my point is -- don't roll your own. Talk to other people who have done similar stuff, and build on their work, otherwise you're liable to make all of the same mistakes, and waste a whole lot of time. And in general (at least ESSI / ESIP-wide), we're a pretty sharing community ... we don't want anyone out there wasting their time doing the stupid little piddly stuff when they could actually be collecting data or doing science.
(and if you haven't guessed already ... I'm an AGU/ESSI member, and I think I'm an honorary ESIP member (as I'm in the space sciences, not earth science) ... at least they put up with me on their mailing lists)
Build it, and they will come^Hplain.
Actually AUFS requires kernel patches, it's never been mainlined because the kernel maintainers like their own union mounts better ... even though they are far less useful (not write-through like AUFS, which is really nice for something like a file server) and forever undelivered. That said, I think Ubuntu and SUSE still come with AUFS patched in ... for Debian you have to compile your own patched kernel or use something like the Liquorix kernel.
Someone please mod this guy up.
I swear, the higher the price of the software is, the more upper management just drools all over it, and the bigger the piece of shit it is. Millions of dollars spent per year licensing some of the biggest turds I've ever had the displeasure of dealing with. Just so management can say that some big vendor is behind it and will "have our backs when it fails".
Guess what, the support is awful too. The vendor never has your back. You'll be left languishing with downtime while they leave you hanging. They don't care because they're so much bigger than your company, and the "license agreement" you signed means you can't hold them responsible for shit. You'd be so much better using some open source software that does pretty much the same thing, and paying some other company to support it on a per-case basis. Take the bags of money you save and hire some devs to code in the missing functionality you need.