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Re: Advice sought : new database server

From: Rory Campbell-Lange <rory(at)campbell-lange(dot)net>
To: Craig James <cjames(at)emolecules(dot)com>
Cc: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>,pgsql-performance(at)postgresql(dot)org
Subject: Re: Advice sought : new database server
Date: 2012-03-05 21:59:00
Message-ID: 20120305215900.GA4579@campbell-lange.net (view raw or flat)
Thread:
Lists: pgsql-performance
On 05/03/12, Craig James (cjames(at)emolecules(dot)com) wrote:
> On Sun, Mar 4, 2012 at 10:36 AM, Rory Campbell-Lange <
> rory(at)campbell-lange(dot)net> wrote:
> 
> > We do have complex transactions, but I haven't benchmarked the
> > performance so I can't describe it. Few of the databases are at the many
> > million row size at the moment, and we are moving to an agressive scheme
> > of archiving old data, so we hope to keep things fast.
> >
> > However I thought 15k disks were a pre-requisite for a fast database
> > system, if one can afford them? I assume if all else is equal the 1880
> > controller will run 20-40% faster with 15k disks in a write-heavy
> > application. Also I would be grateful to learn if there is a good reason
> > not to use 2.5" SATA disks.
> 
> Without those benchmarks, you can't really say what "fast" means.  There
> are many bottlenecks that will limit your database's performance; the
> disk's spinning rate is just one of them.  Memory size, memory bandwidth,
> CPU, CPU cache size and speed, the disk I/O bandwidth in and out, the disk
> RPM, the presence of a BBU controller ... any of these can be the
> bottleneck.  If you focus on the disk's RPM, you may be fixing a bottleneck
> that you'll never reach.
> 
> We 12 inexpensive 7K SATA drives with an LSI/3Ware 9650SE and a BBU, and
> have been very impressed by the performance.  8 drives in RAID10, two in
> RAID1 for the WAL, one for Linux and one spare.  This is on an 8-core
> system with 12 GB memory:
> 
> pgbench -i -s 100 -U test
> pgbench -U test -c ... -t ...
> 
> -c  -t     TPS
> 5   20000  3777
> 10  10000  2622
> 20  5000   3759
> 30  3333   5712
> 40  2500   5953
> 50  2000   6141

Thanks for this quick guide to using pgbenc. My 4-year old SCSI server
with 4 RAID10 disks behind an LSI card achieved the following on a
contended system:

-c  -t     TPS
5   20000  446
10  10000  542
20   5000  601
30   3333  647

These results seem pretty lousy in comparison to yours. Interesting. 

-- 
Rory Campbell-Lange
rory(at)campbell-lange(dot)net

Campbell-Lange Workshop
www.campbell-lange.net
0207 6311 555
3 Tottenham Street London W1T 2AF
Registered in England No. 04551928

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