What Goes into an Enterprise Network?

Komi asks: "I work for a big semiconductor company, and I'm part of a group that is spear heading the Linux movement here. Right now everyone uses Sun machines to design, but you can get a cheaper Linux x86 machine that is four times faster. So it is my job to prove that Linux works. The problem is that I'm an analog circuit designer stuck in the role of sysadmin. So I need some advice on what goes into a network. It won't be that large right now, but it has to be scalable for up to a couple of hundred machines. If this works, then hopefully we'll convince all designers at my company to make the switch."

"Here's the hardware that I am planning on getting:

• 2 servers:
  
  These would hold the home accounts and tools, as well as serve out NIS, NTP, etc. I know I'll need a lot of hard drive space (2x72GB SCSI each), but do I need a lot of memory? (It's 4GB RDRAM max.) Should the processor be fast, or dual?
  
  
• 3 batch machines:
  
  These would be a small compute farm running LFS or something. Jobs would get queued up and run continuously. So these should be dual CPU with lots of memory, probably 4GB each. Any other particular details?
  
  
• 10 desktop machines:
  
  These would be on the designers and developers desktops. These should be reasonably fast (~2GHz) single CPU machines with probably need at least 2 GB RAM. The simulations we run do not benefit from dual CPUs. They probably don't even need SCSI. I'm thinking a $2k PC should work.
  
  
• 1 Itanium server:
  
  This would be to play around on to test our 64-bit applications. The only advantage of 64-bit is applications using huge amounts of data.

We plan to run Red Hat 8.0 on these machines. Is there anything I'm missing? I don't have much redundancy in the servers. I plan to do backups to DVDs. Is this asking for trouble? Any further advice would be appreciated."

Comments

Think TASKS not BOXES!!

[crmartin]

The first thing you've `got to do is stop thinking about how you're going to buy a couple of boxes and that'll make your network, because, Bullwinkle, that trick never works. Except, at least, for those of us who consult for a living, because we often get gigs out of saving someone's shorts from the George Foreman.

Now, back up and think about this:

• who will use the machines on the network?
  
• what will they be doing?
  

In your case, you're talking primarily about engineers, and they are primarily (for job functions) going to be doing engineering ... which means (this is not sarcasm) that they will spend anywhere from 2-4 hours a day interacting with their tools of choice for circuits and engineering, and the remainging time with web browsers, email programs, etc., particularly including word processors or the like. Since you're starting with a Sun network, you at least have confidence that everything people would normally use is UNIX-able.

Now, on you EXISTING network, measure what a few users do for at least a few days. If you've got admin on, you should be able to extract information from the logs. This will give you a chance to get at how much load there really is.

Next task: establish some of your "non-functional" requirements. In particular, how long can response time be for your most important tools, how long can you afford to have the system as a whole be unavailable, and how much work (an hour, half a day, a week?) can you afford to lose. Divide all of those by two and make them your basic "service level agreement" -- which is simply a statement of the service you promise the users, it doesn't have to be fancy.

Here are some reasonable values, from experience, but YMMV: most people will put up with the whole system being unavailable for an hour, they want half-second response time from specialized tools and more like about 4 seconds on a web page, and engineers hate losing ANYTHING but usually don't get too pissed off if it's less than a couple of hours work and doesn't happen very often.

Next: what's the environment? Do you have to think about firewalling yourself from the rest of the network? (Don't assumme just because you're inside the corporate firewall that you're protected. Get AND READ the corporate security policy, as well as talking with the admins who own the network as a whole.) How will you do backups? How do you fit into the corporate disaster planning scheme? (Lots of people forget that one, but just look into what happened to the Wall Street Journal on 9/11 to see how essential it really is.) This analysis will give you a good idea what you need.

And now, having said all that, it will turn out that what you're going to need is (1) a "big enough" file server with 5/4 RAID and a good periodic backup onto "archival media" like tapes or writeable CDs; (2) one workstation good enough for all your applications, and with at least a years' room for growth, for each desktop (plan to buy at leasy one for a spare, and set it up "hot" so a single failure doesn't slow anyone down"); (3) a smallish box as a print server (if you manage your own email, it can often go onto this); and (4) a firewall box or a router (betcha 50 cents Canadian that the company will insist on this.)

Plan for a full week, plus one day per user workstation, for installation. That is, with 4 users, plan on 5 + 4 = 9 days for two people.

All the other stuff, like using NIS, NFS, Kerberos, etc, will more or less fall out if you get these steps right first.