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* local-storage versus SAN sequential read performance comparison
@ 2012-05-21 14:17 Jan Nielsen <jan.sture.nielsen@gmail.com>
0 siblings, 1 reply; 3+ messages in thread
From: Jan Nielsen @ 2012-05-21 14:17 UTC (permalink / raw)
To: pgsql-performance
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
Attachments:
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readahead-sdc.png (image/png, 11.9K) download
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* Re: local-storage versus SAN sequential read performance comparison
@ 2012-05-21 15:41 Scott Marlowe <scott.marlowe@gmail.com>
parent: Jan Nielsen <jan.sture.nielsen@gmail.com>
0 siblings, 1 reply; 3+ messages in thread
From: Scott Marlowe @ 2012-05-21 15:41 UTC (permalink / raw)
To: Jan Nielsen <jan.sture.nielsen@gmail.com>; +Cc: pgsql-performance
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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> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-performance
>
--
To understand recursion, one must first understand recursion.
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: local-storage versus SAN sequential read performance comparison
@ 2012-05-21 15:50 Shaun Thomas <sthomas@optionshouse.com>
parent: Scott Marlowe <scott.marlowe@gmail.com>
0 siblings, 0 replies; 3+ messages in thread
From: Shaun Thomas @ 2012-05-21 15:50 UTC (permalink / raw)
To: Scott Marlowe <scott.marlowe@gmail.com>; +Cc: Jan Nielsen <jan.sture.nielsen@gmail.com>; pgsql-performance
On 05/21/2012 10:41 AM, Scott Marlowe wrote:
> How fast is the link to your SAN? If it's Gigabit, then 80MB/s would
> be pretty reasonable.
Wow, I didn't even think of that. I was looking up specs on the SAN. :)
Those stats are pretty horrible for sequential reads. The SAN should
improve random reads, not mercilessly ruin sequential.
That does sound like the problem, though.
--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-444-8534
sthomas@optionshouse.com
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2012-05-21 14:17 local-storage versus SAN sequential read performance comparison Jan Nielsen <jan.sture.nielsen@gmail.com>
2012-05-21 15:41 ` Scott Marlowe <scott.marlowe@gmail.com>
2012-05-21 15:50 ` Shaun Thomas <sthomas@optionshouse.com>
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