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[K12OSN] Client RAM requirements? / Athalon ATA server vs. Dual-Xeon with SCSI - feedback?



I am getting involved with our local schools to explore the possibility
of a K12LTsP deployment. After some initial reading, it appears for
K12LTSP (2.0.2 ISO's just downloaded) almost any old legacy box can
become a client.

My main question is how much RAM is required?  I should think if
everything runs from the server, even 4 or 8mb RAM would do fine, and
even a pentium 75 with a 2mb DRAM PCI video would perform nicely with a
100bT NIC.  We can most likely make extensive use of existing clients.

Attached is some ballparking I did for a single CPU Athalon Server for a
target of 12 clients utilizing 3 ATA/100 drives and a Dual Xeon for a
target of 24 clients.  The prices come from a little poking around on
pricewatch - with the recognition that we may pay a little more in one
area and skimp a little in another.  My thought is that is due to the
larger storage space per dollar (as well as client) the IDE drives might
be a favorable option over the SCSI drives. 8.7ms seek for 12 clients vs
5.2ms seek for 24 clients is the number that really seems to make this
acceptable - plus the estimated cost per client.  I am also figuring
putting a separate 9 or 10gb drive for a swap-only partition should help
out the whole equation.  128mb/client ought to help reduce swapping in
the first place, until client load gets heavy. Certainly a smaller drive
than a 10gb 7200rpm IDE

The Xeon server could also be built more cheaply - such as 1.7 Xeons, or
even a single CPU Xeon.  From the reading, I've been getting the
impression that CPU load isn't really the performance bottleneck, but
rather the RAM and seek time of hard drives.

I'll be setting up a test K12LTSP server soon at home to play with all
this on a 1.2 Athalon /ATA100 drive and 3 or 4 existing Winboxes of
various speeds, booting to floppy to connect to the server - I'm not up
on how to configure those yet for the various Xf86 drivers, but I'll
read the documentation. :)

Another question, on the site, it was mentioned that 2 SCSI drives were
suggested for the larger server - one for /home, although I think in the
example /home was mounted on another server's SCSI.  I'm thinking
putting /home on the same box should not adversely affect performance
too much.

Finally, and this is a bigger curiosity than some of the others:
Network congestion.  Pushing graphics over a 100bT can get slow.  Not
being too knowledgeable about X, my experience with this is limited to
running VNCserver/client over my 100bT here - but I'm the only user.
With 24 or 32 active clients, isn't the network a limiting factor?
Would performance be noticeably increased with just 12 clients?  

I'd welcome any feedback on these 6 issues as described above:

1) RAM/CPU for clients
2) IDE vs. SCSI
3) Athalon vs. Dual Xeon
4) Separate swap drive - would it help?
5) /home on separate drive on same box
6) Network congestion with 24 or 32 clients vs. 12 clients

Big thanks,

Greg Long
Klamath Linux Unix Group
http://www.maneuveringspeed.com/klug/index.html 
Title: Tables
Sheet1
System 1 CPU Athalon cost
2 CPU Xeon cost
No Clients 12

24








RAM (mb) 1536

2048








Motherboard Abit KT7A ATA100 $92.00
DUAL Xeon w/ SCSI UW + LAN $400.00 (est)
CPU Athalon 2000+ (1.677ghz) $160.00
Dual Intel Xeon 2.0ghz ($280 ea) $560.00
CPU cooler
$15.00 (est) (two) $30.00 (est)
RAM 1.5gb (3 512mb PC133 @ $150ea) $450.00 (est) 3gb (3 1024mb@ $325) $975.00 (est)
Hard Drive 0 (system) Maxtor 60gb ATA133-8.5ms - 7200rpm $95.00
Seagate SCSI UW-5.2ms 18gb - 10000rpm $160.00
Hard Drive 1 (/home) Maxtor 60gb ATA133-8.5ms - 7200rpm $95.00
Seagate SCSI UW-5.2ms 36gb - 10000rpm $270.00
Hard drive 2 (swap) WDC 10gb 8.9ms ATA/100 - 7200rpm $60.00
Seagate SCSI UW-??ms 9.1gb - 10000rpm $90.00
Case
$80.00 (est)
$80.00 (est)
NIC (two) $70.00 (est) 1 extra $35.00
Switch/Hub 16port $80.00 (est) 32 port $291.00
video (any PCI) $15.00 (est) (any PCI) $15.00 (est)




























Total
$1,212.00

$2,906.00







Average cost per client
$101.00

$121.08







RAM (mb/client) 128.0

85.3

Sheet2

Sheet3


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