[K12OSN] Scalability (long email)

Terrell Prude', Jr. microman at cmosnetworks.com
Wed Apr 7 02:33:41 UTC 2004

Understand that you really should have Gig-E on your server, that is, 
the side of it connected to the thin clients.  The reason:  I did some 
measurements a while back.  Running TuxType, X11 sucked up 73Mb of 
bandwidth on a 100BaseTX switched connection...from one client...by 
itself.  Also note that, if you've got a switch that supports Gigabit 
EtherChannel (also called Ethernet trunking or port aggregation), you 
can gang two Gig-E cards together and get 2GB, Full Duplex.  Those from 
3Com and Intel do support this.  Do *NOT* try to run K12LTSP across a 
WAN link, unless your WAN link is Gig-E or an OC-48!

Also understand that DRAM is your saviour.  The more DRAM in particular, 
the better.  This will help your scalability.  In the case of Athlons 
(like mine), 4GB is the limit.  P4 Xeons, I understand, can hit up to 
64GB when using the BIGMEM kernel, using a paging hack similar to the 
old LIM EMS memory specification used back in the MS-DOS days.  Opterons 
can access that and much more--natively, no paging tricks--if your 
kernel is 64-bit.  Therefore, if you're worried about scalability of 
your servers, I would recommend Opterons, specifically, a dual-Opteron 
architecture.  It's not as expensive as you might think, and there is 
now a version of RHEL compiled for AMD64, for $50, if you're an 
educational institution.

As for the Windows-based management program, I'd recommend a separate, 
beefy app server for that.  This is how the City of Largo, FL set up two 
dual-Pentium III servers handling 400 thin clients--they have separate 
app servers for OO.o, WordPerfect, etc.  This offloads their LTSP 
servers big time and is what lets them run so blasted many clients.


>The other option, is to go completely with thin clients in the classrooms -- 
>but then I worry a GREAT deal about scalability and network bandwidth.  
>Management-wise, the thin client solution makes a lot of sense (of course) -- 
>especially since I doubt I'll be having any help from outside hires or 
>teachers with release time.  I really worry about the scalability of the 
>servers and network though... any real world examples I could pull from?

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