[BBLISA] Fileserver opinion

[Bill Bogstad]

On Wed, Aug 11, 2010 at 5:45 PM, Ian Stokes-Rees
<ijstokes at crystal.harvard.edu> wrote:
>> I don't have any advice, but I have a few questions:

>
>> 2) With data spanned over 5 drives, is there still a performance
>> difference between 7,200 rpm and 15,000 rpm drives? Have you the ability
>> to experiment before putting out the cash?
>
> I don't know.  No, we can't test this before purchasing, so any
> experience on this would be appreciated.  Our best guess is that faster
> is faster, and we need faster, but it is a "best guess", hence the
> petition to bblisa.

That's just it.  "faster" isn't always faster.   Higher RPM drives are
typically going to reduce latency, but when you stripe disks you may
not see any improvement in sustained IO throughput.   Is your IO load
random or a few sequential streams?

OTOH,  it may be that $8-10K really isn't enough money to be worth
spending significant time on analysis.  It may be that you don't even
have the kind of info necessary to do this
kind of analysis.  If so, it might be worth thinking about how to
change things when the new system is installed so you don't end up
guessing the next time an upgrade is required...

Bill Bogstad