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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