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Message-ID: <4C4B5984.4010705@gmail.com>
Date: Sat, 24 Jul 2010 23:22:12 +0200
From: Yeb Havinga <yebhavinga@gmail.com>
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To: Greg Smith <greg@2ndquadrant.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Testing Sandforce SSD
References: <4C4A9452.9070100@gmail.com> <4C4B1F84.5030306@2ndquadrant.com>
	<4C4B43DA.90201@gmail.com> <4C4B4512.2060007@gmail.com>
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Yeb Havinga wrote:
> Yeb Havinga wrote:
>> diskchecker: running 37 sec, 4.47% coverage of 500 MB (1468 writes; 
>> 39/s)
>> Total errors: 0
>>
>> :-)
> OTOH, I now notice the 39 write /s .. If that means ~ 39 tps... bummer.
When playing with it a bit more, I couldn't get the test_file to be 
created in the right place on the test system. It turns out I had the 
diskchecker config switched and 39 write/s was the speed of the 
not-rebooted system, sorry.

I did several diskchecker.pl tests this time with the testfile on the 
SSD, none of the tests have returned an error :-)

Writes/s start low but quickly converge to a number in the range of 1200 
to 1800. The writes diskchecker does are 16kB writes. Making this 4kB 
writes does not increase writes/s. 32kB seems a little less, 64kB is 
about two third of initial writes/s and 128kB is half.

So no BBU speeds here for writes, but still ~ factor 10 improvement of 
iops for a rotating SATA disk.

regards,
Yeb Havinga

PS: hdparm showed write cache was on. I did tests with both ext2 and 
xfs, where xfs tests I did with both barrier and nobarrier.