Re: SAN performance mystery

Michael Stone wrote:
> On Mon, Jun 19, 2006 at 08:09:47PM +1000, Tim Allen wrote:
>> Certainly, the read performance of the SATA disk still beats the SAN,
>> and there is no way to lie about read performance.
>
> Sure there is: you have the data cached in system RAM. I find it real
> hard to believe that you can sustain 161MB/s off a single SATA disk.
>

Agreed - approx 60-70Mb/s seems to be the ballpark for modern SATA
drives, so get get 161Mb/s you would need about 3 of them striped
together (or a partially cached file as indicated).

What is interesting is that (presumably) the same test is getting such
uninspiring results on the SAN...

Having said that, I've been there too, about 4 years ago with a SAN that
had several 6 disk RAID5 arrays, and the best sequential *read*
performance we ever saw from them was about 50Mb/s. I recall trying to
get performance data from the vendor - only to be told that if we were
doing benchmarks - could they have our results when we were finished!

regards

Mark