On 11 Nov 98 at 16:11, Drew Dunn wrote:

> An ISP has several sites that get their Internet feed from them.
> To avoid expensive bandwidth issues, they desire to cache web
> requests to those sites.  The problem is that we cannot determine
> exactly what CPU to put in these systems.
>
> Their existing caching server has (effectively) 3 T1's connected
> to it.  It is currently at capacity.  The system will become
> processor bound if any more T1's are connected.  It has a PII-350
> with 512MB of RAM.
>
> The question at hand is, what processor would effectively handle
> four T1 connections?  Would a single PII-450 be effective or will a
> dual PII-350 work?  My calculations show that a PII-450 is roughly
> 23% faster than a PII-350.  If we represent the pooled T1 lines as
> a total bandwidth of 100, I would need a processor that can handle
> a bandwidth of 133.33, but I show that a PII-450 would handle about
> 123.  Is that true?  Should it be more? Less?  If the caching
> software forks processes to multiple processors, would a dual
> PII-350 be more or less effective than a single PII-450?
>
> One concern is that we deliver the best bang for the buck.

  If a single PII-350 handles three lines, dual PII-350s should
handle at least four and maybe five.  Dual 400s should do six, and
*might* get you to seven.

  But are you sure that the process is CPU bound?  Three T1s is only
about 4.65 Mb/s, not much more than you might see from a 10 Mb/s NIC.
I wouldn't think CPU would be your bottleneck.
  Although you've got plenty of RAM, I'd suspect that hard drive I/O
might be a problem.  If you're using IDE/EIDE, try switching to SCSI
(which lowers CPU utilization for I/O).  Consider "striping" drives
to double or triple maximum bandwidth between drives and RAM.  Uner
Win9x, you could fine-tune the amount of RAM used for disk caching;
your question about dual CPUs suggests NT, and I'm not sure if
there's an equivalent parameter there.

David G

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