Re: interesting MD-xfs bug

Roman Mamedov
2015-04-10T04:43:46Z

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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 small‐
est device has been exhausted, the RAID0 driver starts collecting
chunks into smaller stripes that only span the drives which still have
remaining space.

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

--
With respect,
Roman

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