[K12OSN] SATA RAID recommendation for /home server.

[Krsnendu dasa]

I would like some advice on options for optimizing overall LTSP
performance. In particular I am looking at the importance of /home
performance.

I've described everything below. I start general and get more detailed
as I go down.

Key Questions:
How can I improve performance in the most cost efficient way? Cost
efficient not only in dollars spent on hardware but also in time
required to maintain the system.

Where is the bottleneck? Speed of /home drive or ltsp server load (CPU and RAM)?

RAID 1, 10 or 5? I heard 5 has slow seek times. Is that important for
/home on ltsp? Will RAID 10 give me much performance improvement over
RAID 1?

PCI or PCIe – If seek time is more important that throughput, does it
matter if I use a PCI card or a PCIe card?

SITUATION
I am looking to set up a /home server using SATA RAID.
I currently have 2 AMD Athlon 2500XPs with 2GB RAM and 120GB SATA HDs.
I also have an AMD Duron 1.2 with ATA HDs.
The Athlons have PCI 2.2 66MHz bus. Not sure about the Duron (33 or 66MHz)

Options I am considering:

1. Run the Athlon machines in parallel as LTSP servers and get an SATA
RAID card for the Duron to run /home from. Duron would be ldap PDC,
Athlons would be ldap BDCs.
Advantages: Minimal expense /home and authentication load taken away
from ltsp servers.

2. Run the Athlons in parallel and let one host /home in a raid 1
arrangement? With the other one running BackupPC (with backups to its
own HD). Ldap set up in failover arrangement.
Advantage: Cheapest option, only 2 virtually identical machines to maintain.
Disadvantage:/home speed not maximized

3. Same as 2 above but install SATA RAID card for /home in one machine.
Advantage: /home might be faster on separate channel (but probably
limited by 66MHz bus)
Disadvantage: /home load still on ltsp server.

4. Run one Athlon as the ltsp server and the other as the /home
server. Ldap set up in failover arrangement.
Advantage: /home speed should be faster
Disadvantage: LTSP redundancy and load-bearing features lost. Less RAM
for LTSP and probably too much for /home machine.

5. Use the Duron just for BackupPC and maybe Winxp in Vmware
Advantage: More secure backup. Takes BackupPC load away from LTSP servers.
Disadvantage: Slower processor of Duron may affect BackupPC
performance. Another machine to maintain for little performance gain.

BACKGROUND
Environment:
Primary school (Ages 5-13years old) Roll: <100 students
Number of terminals: Total 26
24 terminals in classrooms (divided into 4 classes – used at various
intervals throughout the day.)
1 in the library (rarely used)
1 used for administration (constantly used)
Other computers:
5 Windows laptops (occasional access to shared files on /home)

Typical usage:
Gnome desktop
Junior Class (5 computers): GCompris, TuxPaint, Online Flash games
Other Classes: Online Flash games, OpenOffice.org, Scribus (occasionally)
Office: MSExcel, MSWord, MSAccess, MYOB (all under Crossover Linux)
Firefox, Rhythmbox, TerminalServer Client

Current server setup:
Standalone Firewall and Internet filter (IPCop)
K12LTSP-6 plus a few extra services:
BackupPC (backs up to its own hard drive in the K12LTSP box.)
VMware Server running Windows XP (for legacy accounting application
MYOB that doesn't print properly under Crossover Linux)
FreeNX server (Mostly used by me to access system from home and from
my Windows laptop at school.)


Currently used Hardware:
IPCOP: PII 350
K12LTSP:AMD2500XP 2GB RAM 120GB SATA HD + 250 GB SATA for Backups

Available Hardware:
AMD2500XP 2GB RAM + 2 x 120GB SATA HD (Same motherboard as other
computer.) PCI 2.2
AMD Duron 1.2GHz  + ATA HD