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Re: [K12OSN] Just about ready to make a purchase



On Tue, 2007-05-08 at 22:43 -0700, Robert Arkiletian wrote:
> On 5/8/07, Jim Kronebusch <jim winonacotter org> wrote:
> > I am finally ready to purchase the new server for our school and new thin clients.
> > Below is what we'll be starting with, making the switch on labs and media centers first,
> > next year adding teachers.
> >
> > -Dell PowerEdge 6800
> > -Quad 3Ghz/800Mhz/4mb Cache Dual Core Intel Xeon 7130 Processors
> > -16MB 400Mhz DDR2 RAM (8x2GB to start, will handle 64GB total)
> > -Embedded PERC4e/Di RAID Controller
> > -6 300GB 10K RPM Ultra 320 SCSI hard drives configured in RAID 10 (3 striped 300GB
> > mirrors for a total of 900GB storage, machine will handle 10 SCSI drives and a 2 drive
> > media bay for future expansion, from my research this will give me the fastest possible
> > read/write speeds while maintaining full hot swap redundancy)
> 
> Your post stuck in my head this evening Jim. Few more points I wanted
> to share. Those 8 cores are fed by (share) one 800Mhz FSB memory
> controller using UMA (Uniform Memory Access). This is where Opteron
> systems shine. Each Opteron has it's own memory controller. So you
> would have 4 memory controllers controlling 4 memory banks. However, I
> am not sure if NUMA (Non Uniform Memory Access) in the Linux kernel
> works with dual core cpu's. Maybe someone can chime in if they know.
> But I know 4 single core cpu's would enable NUMA support.

NUMA works with dual cores but it has no effect on a single chip dual
core as both cores already access the same RAM bank.

Opterons kick some serious bits when it comes to RAM access. During
testing prior to the APS installation, I determined that a single chip
dual core 2.6 GHz Opteron could perform about 30% faster than the same
setup with a dual core 2.8 GHz Xeon. Same hard drives (Ultra 320) and
both with 1GB RAM (and both HP servers running K12LTSP 5 beta 9). Using
teachertool, I launched 24 simultaneous oowriters. Th Xeons took 71
seconds while the Opterons only required 48. The numbers were more
dramatic on a reload (i.e. load, close and reload all 24 to run from
cache RAM). Xeon clocked in at 26 seconds while the Opterons smoked in
at just under 13!
> 
> >From http://en.wikipedia.org/wiki/Non-Uniform_Memory_Access
> 
> "Now a system can starve several processors at the same time, notably
> because only one processor can access memory at a time.
> 
> NUMA attempts to address this problem by providing separate memory for
> each processor, avoiding the performance hit when several processors
> attempt to address the same memory. For problems involving spread data
> (common for servers and similar applications), NUMA can improve the
> performance over a single shared memory by a factor of roughly the
> number of processors (or separate memory banks)."
> 
> However, the shared memory portion of something like Firefox will
> still probably use AMD's Hyper Transport bus.
> 
> BTW, 300GB scsi drives are awful expensive. If you are going to use
> hardware RAID 10 have you considered enterprise SATA drives and a
> dedicated PCI-X SATA controller with onboard write back cache (3ware
> 9550SX or LSI MegaRAID 300-8X). My guess is it would probably be
> better than the controller that comes with the Dell. Maybe someone who
> has used those controllers can comment.
> 
> Just checked the Dell PowerEdge 6800 specs and they have this under
> the power supply section.
> 
> "Redundant power is available in all 200-240V configurations and most
> 100-119V / 120-127V configurations except those that contain or exceed
> four processors, 32GB memory, five hard drives, and two PCI cards.
> Redundant power availability will vary by configuration. NOTE: The
> minimum configuration for most US based facilities is 120-127 Volts."
> 
> According to this, your setup probably requires too much power to
> support redundancy.
> 
> -- 
> Robert Arkiletian
> Eric Hamber Secondary, Vancouver, Canada
> Fl_TeacherTool http://www3.telus.net/public/robark/Fl_TeacherTool/
> C++ GUI tutorial http://www3.telus.net/public/robark/
> 
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> 
-- 
James P. Kinney III          
CEO & Director of Engineering 
Local Net Solutions,LLC        
770-493-8244                    
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney localnetsolutions com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7

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