Re: RAID10 - Ensure mirrors aren't on same JBOD

[Keld Simonsen <keld@keldix.com>]

On Mon, Apr 26, 2010 at 11:57:09AM -0700, Andrew Klaassen wrote:
> --- On Mon, 4/26/10, Michael Evans <mjevans1983@gmail.com> wrote:
> 
> > > --- On Mon, 4/26/10, Michael Evans <mjevans1983@gmail.com>
> > wrote:
> > > However, it doesn't say what happens with a larger
> > > number of drives.  I'm looking for the kind of control I
> > > can get with RAID 1+0, where I can specify which drives are
> > > mirrors of each other.  Is that possible with RAID10?
> > 
> > No, not predictably; the only provided guarantee is that
> > the data will
> > /not/ be duplicated on the same block-device (usually
> > drive).  In
> > practice you will quickly be able to determine where a
> > particular
> > version with a given range of input causes data to be
> > stored, but
> > there is no requirement that future versions produce the
> > precise same
> > alignment and offsets.
> 
> Ah.  So if I want this level of control, I have to sacrifice the advantages of RAID 10 and go with RAID 1+0.
> 
> Good to know.  Thanks.


I think you can control the exact layout of copies in raid10 at creation time for
the raid. How exactly it will play I am not sure - maybe Neil can tell us.

Anyway you should be able to use raid10 as one of the components in a raid 1+0 like scenario, eg as
the raid1 part of the raid 1+0.

best regards
keld
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