Dear Neil,
> > Unfortunately shrinking the raid10-array back to 13 devices
> > does not work:
> >
> > # mdadm --grow /dev/md5 --array-size 12696988928
> > # mdadm --grow /dev/md5 --raid-devices=13
> > mdadm: Cannot set array shape for /dev/md5
>
> Where did you get that array-size from? It isn't a multiple
> of 512K. Hence the chunksize setting reports an error.
mdadm told me to use this :-)
Here's what I did:
# mdadm --detail /dev/md5
..
Array Size : 15627063296 (14903.13 GiB 16002.11 GB)
Used Dev Size : 1953382912 (1862.89 GiB 2000.26 GB)
Raid Devices : 16
..
Note: 15627063296 = 1953382912 * 16 / 2
Now if I reduce the number of devices to 13 mdadm complains
about the array-size and suggests a value to use:
# mdadm --grow /dev/md5 --raid-devices=13
mdadm: this change will reduce the size of the array.
use --grow --array-size first to truncate array.
e.g. mdadm --grow /dev/md5 --array-size 12696988928
mdadm calculates the new array-size from the componentsize
by multiplying it with 13 and dividing it by 2:
newarraysize = componentsize * 13 / copies
While the old array-size is a multiple of 512 the new is not.
So I truncated the array to the size of the underlying
filesystem (which is 12696988672K, a multiple of 512K)
and that worked.
Thanks again for your support
Peter
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