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Date: Tue, 26 Jun 2007 16:54:05 +0200
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To: Ivan Voras <ivoras@fer.hr>
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Cc: freebsd-geom@freebsd.org
Subject: Re: gjournal performance issues
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Ivan Voras wrote:
> Fluffles wrote:
>
>> First, my setup:
>> 8 disks in RAID5 using geom_raid5, gjournal on top where both the 
>> journal (1GB) and the data is stored on the same consumer. Since 
>> gjournal uses both metadata and file/dir for journaling, this means 
>> that, theoretically, the write speed of sequential operations is 
>> doubled. Unfortunately, it appears to have crashed.
>
> Just to rule out geom_raid5, can you repeat your tests with geom_raid3?

Sounds logical. But: RAID3 does not have any 2-phase writes, all writes 
are 1-phase, involving all disks. Thus RAID3 would be less affected by 
non-contigious writes. I will test with debuglevel or with geom_nop to 
see the I/O that geom_journal produces, and to see if this I/O is 
contigious or not. I hope to know more in a day or so.

Thanks for your input Ivan and Pawel! More testing is needed...

- Veronica