[K12OSN] Blade Server for LTSP?

"Terrell Prudé Jr." microman at cmosnetworks.com
Tue Mar 13 16:14:09 UTC 2007

Jim Kronebusch wrote:
>> One point though...Is it really necessary to have LDAP and mail on a
>> different blade? With even 5000 accounts (let alone 500) mail should
>> not put very heavy load?
> I doubt it.  In the past I have ran mail along with many other things.  The
> only time I have seen a difference is when my file server also is hosting
> email and large transfers are happening (sometimes can bring webmail to a
> halt).  Also I use heavy screening for SPAM and Viruses, sometimes MailScanner
> alone can put 30% load on the server.  Main reason I want to break things down
> is I am sick of playing games when doing upgrades.  Say I have one server
> running LDAP, file serving, mail, web, etc I have many more factors to weigh
> when doing upgrades.  That is the only reason I am looking at breaking things
> down more.  Most likely the final result will be to have my LDAP and email on
> the same server.

True, email itself doesn't require a lot of oomph.  I've run 500 users
on a Sun Ultra 5 back in the day (Postfix + Courier-IMAP) without
stressing the box.  However, I still prefer to have email on a separate
box.  The reason for that is security.  If the cracker compromises one
daemon (e. g. sendmail), he doesn't own a bunch of other stuff, too.

For stuff like LDAP, email, and Web servers (relatively low CPU
requirements), I'd start looking at one of IBM'S POWER5 boxes that let
you do LPAR's.  Yes, the mainframe LPAR ability now exists at the
microcomputer level.  With such a box, you can make LPAR's as small as
1/10th of the CPU, and you can make your LPAR resource allocation
somewhat dynamic, if you wish, to adjust for changing
requirements/loads.  LDAP can go in one LPAR, email in another one, Web
in another one, etc.  For those who aren't familiar with LPAR's, think
of it as having sort of an "unlimited-license VMware", but built into
the hardware; you have separate "virtual machines."  And yes, they run
GNU/Linux beautifully.

That's how I'd be looking at consolidation.  The POWER5 boxes ain't
cheap, but neither is a good multi-core x86-64 server.

> Could be neat.  But for $7400 I can buy a stand alone Dell 1900 with dual
> Intel Quad Core 2.33Ghz 1333Mhz FSB processors, 16GB RAM, mirrored SAS 36GB
> drives, connect my existing powervault 220s for /home, and 2 dual GB NIC's
> teamed for load balancing.  Where as the chassis for the blade server is $7500
> or so alone + the cost of each blade.

We have a bunch of Sun "blade" servers doing a certain task.  They do
work, but yes, it was very pricey.  Additionally, they've proved to be
more susceptible to breaking; we've had to RMA quite a few of them. 
We're gradually moving back to discrete 1U rack-mount boxes for both of
these reasons--cost and reliability.

> So at this point I am considering the above server to run as my all in one
> LTSP server for 100 clients to start, keep my current Dual Xeon 3Ghz 4GB RAM
> box as my mail/LDAP server and then just add more app servers down the road
> for any apps that drag the thing down.

If you're doing any sort of video streaming, I'd do a load test before I
bought that server if I were you.  In another (recent) thread, a guy in
Atlanta deploying LTSP ran into a CPU bottleneck on his servers because
he's trying to stream video to 90 clients per server.

> I also can't decide if I should just buy all new terminals right away, or just
> run my iMacs as clients and replace as they die.

Why replace something that works?  Isn't that one of the major points of
LTSP--you *don't* need to stay on the "upgrade treadmill" like with
Wintel?  I'd keep those iMac clients and replace them as they die. 
That's what they do in Largo, FL with their thin clients.

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