Hardware Recommendations for LTSP

[Steve]

Are you sure the cost savings over SCSI RAID are _really_ there?  How much 
mass storage do you need?  I bought 15 18GB U160 scsi drives on ebay for 
$130ea and then got a 64bit PCI AMI MegaRAID Elite 1600 for $350.  The nice 
chassis was about $250.  Add a couple cables and terminators at about $150 
and I have ~200GB U160 SCSI RAID 5 (3 separate arrays on their own 
channels) in a 64bit PCI slot.  This thing screams and the CPU is doing 
nothing for the RAID I/O.  My backup is a Sony DDS3 DAT (12/24GB) 
drive.  It works wonderfully with tar.  The advantage of SCSI that I would 
think would benefit you is hardware error detection/correction.

RAID 5 does nothing to improve performance.  It has to do a parity 
calculation and there is some overhead in this.  SCSI RAID off loads this 
to the RAID controller CPU.  I would think the cache on the controller 
would probably offset this loss.  The memory interleaving of the AMI 
controllers would probably go even further to offsetting that.  One last 
benefit of the SCSI solution is the MegaRAID driver is very well developed 
in linux.

I'm pretty sure "bonding" ethernet interfaces is going to require the 
switch to participate in that bonding.  We do it with one of our Cisco 
switches and a 4 port nic in one server.  After setting it up, it seems 
that gigabit ethernet would have been a better way to go.  Switch fabric is 
also going to be a concern here.

Anyway, just my opinions and observations.

>Are you sure?  IDE RAID 0 can easily hit 55-70MB/sec thru-put on two 7200
>rpm disks.  True that isn't redundant, but IDE RAID 5 (3 disk) can do about
>45-55MB/sec.  IDE RAID lacks the onboard cache of *real* SCSI RAID
>controllers, and CPU usage is much higher, but I think the cost/performance
>tradeoff is worth it.  Most of the time I'm looking at this 1GHz CPU Linux
>machine (with one disk), and the bottleneck always appears to be the disk
>clicking away, with 5% CPU usage.  The LTSP servers will be dual 1GHz, so
>I'm sure it can handle the extra overhead just fine.
>
>With the cost savings over SCSI RAID, we could probably afford a Platypus
>battery backed RAM drive.  350MB/sec Reiserfs journal.  Whoopass.