How fast is the link to your SAN? If it's Gigabit, then 80MB/s would
be pretty reasonable.
Also SANs are normally known for very good random access performance
and not necessarily for fast sequential performance.
On Mon, May 21, 2012 at 8:17 AM, Jan Nielsen
<jan.sture.nielsen@gmail.com> wrote:
> This is outside of PG performance proper, but while testing pg_dump and
> pg_restore performance on local-storage versus SAN storage I noticed a big
> performance drops on in the SAN configuration. I'm told that both local
> storage and SAN storage are 15k drives with local-storage running dual RAID1
> configuration while HP StorageWorks SB40c SAN is 10x15k RAID1+0. Running a
> hdparm -tT tests with different read-ahead, I see the following differences
> on /dev/sda (local-storage) and /dev/sdc (SAN storage). I'm shocked at the
> drop in buffered disk read performance 150MB/sec versus 80MB/sec and
> surprised at the SAN variability at 1MB/sec versus 10MB/sec, local-storage
> and SAN storage respectively.
>
> For those who, unlike me, have experience looking at SAN storage
> performance, is the drop in buffered disk reads and large variability the
> expected cost of centralized remote storage in SANs with fiber-channel
> communication, SAN fail-over, etc.
>
> If you have any ideas or insights and/or if you know of a better suited
> forum for this question I'd sure appreciate the feedback.
>
>
> Cheers,
>
> Jan
>
>
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