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Re: Best OS & Configuration for Dual Xeon w/4GB &

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: Luke Lonergan <llonergan(at)greenplum(dot)com>
Cc: Miguel <mmiranda(at)123(dot)com(dot)sv>,Postgresql Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Best OS & Configuration for Dual Xeon w/4GB &
Date: 2006-03-21 11:49:37
Message-ID: 20060321114937.GL15742@pervasive.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Mon, Mar 20, 2006 at 01:27:56PM -0800, Luke Lonergan wrote:
> >> Transfer rates:
> >>        outside:       102400 kbytes in   2.075984 sec =    49326 kbytes/sec
> >>        middle:        102400 kbytes in   2.100510 sec =    48750 kbytes/sec
> >>        inside:        102400 kbytes in   2.042313 sec =    50139 kbytes/sec
> >> 
> > I have 6 ultra a320 72G 10k discs
> 
> Yah - ouch.  With 6 drives in a RAID10, you should expect 3 drives worth of
> sequential scan performance, or anywhere from 100MB/s to 180MB/s.  You're
> getting from half to 1/3 of the performance you'd get with a decent raid
> controller.
> 
> If you add a simple SCSI adapter like the common LSI U320 adapter to your
> DL380G3 and then run software RAID, you will get more than 150MB/s with less
> CPU consumption.  I'd also expect you'd get down to about 2ms access times.

FWIW, here's my dirt-simple workstation, with 2 segate SATA drives setup
as a mirror using software (first the mirror, then one of the raw
drives):

decibel(at)noel(dot)2[5:43]~:15>sudo diskinfo -vt /dev/mirror/gm0
Password:
/dev/mirror/gm0
        512             # sectorsize
        300069051904    # mediasize in bytes (279G)
        586072367       # mediasize in sectors

Seek times:
        Full stroke:      250 iter in   1.416409 sec =    5.666 msec
        Half stroke:      250 iter in   1.404503 sec =    5.618 msec
        Quarter stroke:   500 iter in   2.887344 sec =    5.775 msec
        Short forward:    400 iter in   2.101949 sec =    5.255 msec
        Short backward:   400 iter in   2.373578 sec =    5.934 msec
        Seq outer:       2048 iter in   0.209539 sec =    0.102 msec
        Seq inner:       2048 iter in   0.347499 sec =    0.170 msec
Transfer rates:
        outside:       102400 kbytes in   3.183924 sec =    32162 kbytes/sec
        middle:        102400 kbytes in   3.216232 sec =    31838 kbytes/sec
        inside:        102400 kbytes in   4.242779 sec =    24135 kbytes/sec

decibel(at)noel(dot)2[5:43]~:16>sudo diskinfo -vt /dev/ad4
/dev/ad4
        512             # sectorsize
        300069052416    # mediasize in bytes (279G)
        586072368       # mediasize in sectors
        581421          # Cylinders according to firmware.
        16              # Heads according to firmware.
        63              # Sectors according to firmware.

Seek times:
        Full stroke:      250 iter in   5.835744 sec =   23.343 msec
        Half stroke:      250 iter in   4.364424 sec =   17.458 msec
        Quarter stroke:   500 iter in   6.981597 sec =   13.963 msec
        Short forward:    400 iter in   2.157210 sec =    5.393 msec
        Short backward:   400 iter in   2.330445 sec =    5.826 msec
        Seq outer:       2048 iter in   0.181176 sec =    0.088 msec
        Seq inner:       2048 iter in   0.198974 sec =    0.097 msec
Transfer rates:
        outside:       102400 kbytes in   1.715810 sec =    59680 kbytes/sec
        middle:        102400 kbytes in   1.937027 sec =    52865 kbytes/sec
        inside:        102400 kbytes in   3.260515 sec =    31406 kbytes/sec

No, I don't know why the transfer rates for the mirror are 1/2 that as the raw
device. :(
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461

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Subject: Re: planner with index scan cost way off actual cost,
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