[K12OSN] Just about ready to make a purchase

[Jim Kronebusch]

> > -16MB 400Mhz DDR2 RAM (8x2GB to start, will handle 64GB total)
> 
> 16GB  is more than you need for 90 clients.

That is the plan.  I want to overkill if at all possible.  There is no such thing as too
fast as far as I am concerned.  If it handles 90 clients well, than we will add more
until we see a undesirable decrease in performance.

> > -Embedded PERC4e/Di RAID Controller
> 
> Is this a real hardware RAID controller?
> Is this is a dual scsi interface controller?
> Software or Hardware RAID?
> Make sure half your mirror in the raid 10 is on one scsi interface. If
> you lose one scsi channel you don't want to lose data from both sides
> of your mirror.

It is a hardware RAID.  I have always had real good luck with PERC RAID devices.  The
drives will attach to the hot swap backplane.  As far as I know every Dell backplane I
have messed with only has one connector to go to the controller.  So all drives will be
handled by a single interface.  I can see where there would be a benefit of having the
opposite mirror halves on a separate interface, never thought of that.  Unfortunately I
don't think this is possible with any of the Dell backplanes.  I should probably just
have an add-in controller on hand just in case the controller would die.

> Will your controller handle that many drives? 320 per channel can get
> saturated with 4 fast drives working full bore. So the controller
> might max out at around 8 drives.

I guess I have put my faith in Dell there.  This is their fastest single server
available (at least that I found).  It is supposed to be for high end database
applications with large data throughput and a ton of processor usage.  Since they build
the backplane to handle 10 drives I assume the hardware is meant to handle it.  I do
have an external PowerVault 220S with 6 drives in it right now and it seems to handle
large data transfers well over a single RAID channel.  I wish I had a crystal ball and
could see into the future to know if it will handle all of the thrashing of a possible
90 concurrent users and maybe even another 60 teachers mounting /home over NFS.  If need
be I will use my PowerVault as well and put some users on that and some internally, I
just want to keep this as simple and self contained as possible.  Every time I try and
spread services over multiple servers things seem to slow down.

> Does NIC bonding work well for you Jim? I have heard that it does not
> scale well. ie 2 bonded nics don't equal 2x performance. You might
> want to look at separate subnets on each NIC connected to physically
> separate switches as a means of addressing bottlenecks.
> http://k12ltsp.org/mediawiki/index.php/Technical:Subnetting

It has in the past, but I haven't used it in a heavy LTSP situation.  As far as file
servers go it has worked great for me.  I have only tried with 2 nics in the past, never
tried 4.  With ALB I don't get 2GB throughput on a single connection, but I can get what
seems close on multiple connections.  If anyone has a good suggestion for how to monitor
this I can give a shot at pulling down some hard numbers.  

> > -64 Bit XUbuntu with LTSP 4.2 (I am thinking XUbuntu will give me some extra speed 
> I would seriously consider K12LTSP 5.0EL (which uses LTSP 4.2) based
> on Centos/RHEL 5 for this setup. Support lifetime and
> reliability/support for server grade hardware.

I have been going back and forth on this one.  I really like the pre-bundled out of the
box nature of K12LTSP and the 5.0EL edition gives me the 64-bit support.  But I have
really gotten used to the extremely large software repository of Ubuntu.  Does
fl_teachertool work under other distros such as Ubuntu+LTSP 4.2?  If not that would be
the deciding factor to stick with the packaged K12LSTP.  I will most likely build the
server both ways if I am still undecided and test, then make a final decision.  I will
have a month or so for testing before going live.

Thanks for the input.  I have more to consider.  I just know that at some point I have
to go for it and stop considering :-)

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