Re: Looking for advice on creating XFS on a large (to me) RAID

[Krzysztof Adamski <k@adamski.org>]

On Thu, 2011-11-03 at 13:14 -0400, Christoph Hellwig wrote:
> On Thu, Nov 03, 2011 at 12:29:58PM -0400, Krzysztof Adamski wrote:
> > Hi All,
> > 
> > I'm about to create a XFS file system on a MD RAID6 made up of 12 3T
> > drives.
> > 
> > This is the command line that I was planning to use:
> > 
> > -s size=4096
> 
> using a sector size larger than the actual disk sector size might risk
> data loss, as the log code expects sector sized writes to be atomic.
> 
> If you have a real 4k logical sector disk it should be picked up
> automatically with the kernel topology support.  We don't quite do the
> right thing for 512 byte logical / 4k physical disks, in which case
> you might need this line.

The drives I'm using are Hitachi H3IK30003272SW (0S03208) 3TB, I belive
they are the 512 byte logical / 4k physical disks.


> >          =                       sunit=128    swidth=1280 blks
> 
> In general you're better off with a 32k stripe unit / chunk size,
> than the extremly large default of 512k.

I'll compare a simple dd benchmark of the raw md device with 32k and
512k and report back. The resync takes over 23 hours :-(

Thanks for the info.
K