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Re: How do I tell if my partition is aligned for a 64k/RAID-6?

To: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Subject: Re: How do I tell if my partition is aligned for a 64k/RAID-6?
From: "Josef 'Jeff' Sipek" <jeffpc@xxxxxxxxxxxxxx>
Date: Sat, 27 Dec 2008 08:38:24 -0500
Cc: Michal Soltys <soltys@xxxxxxxx>, linux-raid@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <alpine.DEB.1.10.0812251846270.32331@xxxxxxxxxxxxxxxx>
References: <alpine.DEB.1.10.0812250821360.31386@xxxxxxxxxxxxxxxx> <495410F4.5010508@xxxxxxxx> <alpine.DEB.1.10.0812251846270.32331@xxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Thu, Dec 25, 2008 at 06:46:37PM -0500, Justin Piszcz wrote:
> On Fri, 26 Dec 2008, Michal Soltys wrote:
> >> I am not worried about the filesystem as the defaults usually get it right 
> >> but with parted, this is the first time I had to use it for home use and 
> >> with RAID-6 I am noticing slower performance with 15 disks (1 is a spare) 
> >> in RAID-6 (albeit slower 7200 ones, RE3s) than I was getting with 10 
> >> raptor150s in RAID-6 (but I had used fdisk there).
> >> 
> >> Justin.
> >> 
> >
> > For best effect - partition should start at 1920th sector (stripe width
> > boundary), and su/sw should be appropriately set - su=64k,sw=13 in your
> > case. Parted shows the values normally - from the beginning of the volume, 
> > 0 
> > based.
> >
> >
> > ps.
> >
> > I dropped some of CCs.
> 
> Thanks.

It looks like you made why big partition. Why bother with partitioning at
all? If you just use the whole device, you _will_ be aligned properly if you
tell mkfs.xfs about the stripe unit/width.

Josef 'Jeff' Sipek.

-- 
All science is either physics or stamp collecting.
                - Ernest Rutherford

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