On Dienstag, 20. Juli 2010 Andrew Debenham wrote:
> I'm am new to XFS and am in the process of trying to tune an XFS file
> system. I spent some time searching through this mailing list's
> archives but wasn't able to find anything that matched the question
> that I have (I apologize in advance if this issue has already been
Thanks for reminding me, wanted to write a FAQ entry, done now:
> I have a 3ware 9650SE-12M installed and have a RAID6 unit with 11 x
> 1.82 TB SATA drives and stripe size of 256KB. I found an earlier
> thread that discussed calculating the values for sunit and swidth
> for RAID5, which stated that the swidth would be "sunit x (# disks
> in stripe - 1)". So, finally the question - would the swidth for a
> RAID6 volume be "sunit x (# disks in stripe -2)?
> If that is the case, then here is what I would expect my values to
> be: sunit = 512
> swidth = 4608
I think sunit should be as big as the RAID controllers stripe size, as
it describes the smallest I/O XFS should do. So sunit=512 would make it
possible that XFS writes a single sector, while the RAID controller
needs to read/write 256KB with your stripe size, resulting in
performance degradation. But I'm no XFS dev, so maybe wait for a
clearing from someone who has deeper XFS knowledge than me.
Would be my suggestion for your setup.
mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc
it-management Internet Services
http://proteger.at [gesprochen: Prot-e-schee]
Tel: 0660 / 415 65 31
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