From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roman Mamedov <rm@romanrm.net>
Subject: Re: interesting MD-xfs bug
Date: Fri, 10 Apr 2015 09:43:36 +0500
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To: Dave Chinner <david@fromorbit.com>
Cc: NeilBrown <neilb@suse.de>, Joe Landman <joe.landman@gmail.com>, linux-raid <linux-raid@vger.kernel.org>, xfs <xfs@oss.sgi.com>
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On Fri, 10 Apr 2015 11:31:57 +1000
Dave Chinner <david@fromorbit.com> wrote:

> RAID 0 on different sized devices should result in a device that is
> twice the size of the smallest devices

> Oh, "RAID0" is not actually RAID 0 - that's the size I'd expect from
> a linear mapping.

> it's actually a stripe for the first 10GB, then some kind of
> concatenated mapping of the remainder of the single device.

It might be not what you expected, but it's also not a bug of any kind, just
the regular behavior of mdadm RAID0 with different sized devices (man md):

       If devices in the array are not all the same size, then once the sma=
ll=E2=80=90
       est device has been  exhausted,  the  RAID0  driver  starts  collect=
ing
       chunks  into smaller stripes that only span the drives which still h=
ave
       remaining space.

Once or twice this came VERY handy for me in real life usage.

--=20
With respect,
Roman

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