I run an LTSP setup for work. It was originally approved so that all our basic-needs users can be provided for cheaply and easily, but has expanded over time as it's proved reliable, fast, and cheap. When we first decided to run an LTSP system, we went the whole hog on the server side - and have not regretted it.

We bought a dual 2.4GHz Xeon with 2GB of RAM and Serial ATA RAID (3ware Escalade 8500). The OS and /var (databases + mail) are stored on a RAID 1 array (2x80GB SATA), while user data is stored on a 3x120GB RAID 5 array (soon to be 4x250GB).

The server is, in addition to being a terminal server, the core server for our network - NetATalk (Apple) and Samba (Windows) file sharing, Cyrus IMAPd for IMAP/POP, sendmail for SMTP, MySQL, etc. We also have hundreds of gigabytes of regularly accessed "hot" archival data on the system. It handles all of this, and 20 terminal users, without any noticeable slowdown. Real RAM usage rarely goes above 750mb, and I expect I could pack at least 60 users onto it - and many, many more with more RAM.

The workstations are P133s with 32mb of RAM and S3 video. GOOD VIDEO CHIPSETS ARE VERY IMPORTANT - AND S3 IS NOT A GOOD ONE. A p133 with a GeForce4 MX feels _much_ faster than a P300 with an S3 video card. Keep this in mind when buying workstations - the video chipset (or XFree86 driver quality) seems to be the #1 performance factor. It's also important for the useability of many apps to have at least a 1024x768x16bit display.

Make sure you have good NICs - we use Intel EtherExpress Pro/100s with PXE-enabled flash here.

Additionally, if you want quick user acceptance of the new system, providing quality monitors and optical mice with scroll wheels seems to help a _lot_, especially if they were working with blurry monitors and worn out serial mice before. Users notice and care about different things to many techies - "wow, my screen's so /nice/" will be the deciding factor for many (not quite clicking that the screen is nice on any computer). We actually introduced the system progressively, and by the time about 1/3 of the users had been moved over from the 486/16MB+Win95 systems the rest were almost banging down my door. Why? Because when we upgraded the users' systems, they got quiet desktops, new screens, and nice new mice. The OS? They didnt' care so long as it did what they wanted, which it did.

Overall we've been very satisfied with our system. We'll be migrating the users from XFCE4+Mozilla+OO.o to GNOME2.4+Evolution+OO.o very soon, as the latter is much more useable and much more consistent. Evo is also much less buggy than Mozilla Mail. XFCE4 was great for our basic users, as there were only a couple of things they could click on and it was easy to centrally configure - but now we're moving the journalists onto the system and they want a bit more power. It seems better to put everyone on GNOME than have two diferent environments to support.

I strongly recommend 3ware SATA RAID cards to anyone building such a server, too. They're wonderful in that while they're fast hardware RAID cards, you can add huge amounts of storage for peanuts. If you put the OS, /var and /opt on a couple of Western Digital Raptors (73GB 10,000 RPM SATA drives with TCQ) your server will probably just /fly/. I'm getting good enough results with the current 7200rpm non-TCQ drives we're using, but I hear great things about the Raptor series. They're also _much_ cheaper than SCSI, and according to folks like storagereview.com, they're at least as fast.

Also, for things like terminal servers, the difference a second CPU makes is incredible. We actually have SMT/HyperThreading enabled, so we get 4 virtual CPUs - and absolutely amazing performance when multitasking. This is good when you have 20+ active users doing highly interactive tasks. I strongly recommend choosing an SMP system - they're not /that/ much more expensive, and will prove to support a lot more users.

Also, I second others' comments here: your Xeon should go above 4GB of RAM. Most Xeon boards go to 8GB or 16GB, with the Xeon MP boards sometimes going higher still. We have _lots_ of room to grow with ours, as our server will happily support at least 8GB of RAM.

Speaking of RAM - more is better. 2GB is a good start. What isn't in direct use by processes will be used as disk cache, reducing the load on your disks and making performance very snappy.

One other thing that's of note is that AFAIK Linux will actually only load the binaries and libraries for a program once. You have _one_ copy of libc6 in memory, _one_ copy of OpenOffice, etc. In addition to the memory savings (extra users after the first one cost a lot less in memory, esp with GNOME, OO.o and other memory-hungry apps) you'll notice that apps start a _lot_ faster for the second and subsequent users, because they're already in memory in a useble form.

One other experience: I found that I needed to steer clear of GDM2 in favour of KDM, as GDM2 sometimes hung and stopped responding to connections. Perhaps this has been fixed since Red Hat 8's GNOME (which we're currently using).

On the business side, our LTSP deployment has saved us a lot of money. From AU$1200 for a workstation (with OS and virus scanner) we can now get new workstations for $500 with a decent monitor, or as low as $200 for a quiet, cleaned up 2/h PC. We no longer pay OS upgrade fees, we don't have to worry about CALs, and the (very affordable - thanks to the wonderful ClamAV and MimeDefang developers) virus scanner running on the server is only to protect the legacy win98 users on our network.

Craig Ringer
IT Manager
POST Newspapers