On Monday June 19, Paul.Davidson@xxxxxxxxxx wrote:
> Hi,
>
> I'd like to shrink the size of a RAID5 array - is this
> possible? My first attempt shrinking 1.4Tb to 600Gb,
>
> mdadm --grow /dev/md5 --size=629145600
>
> gives
>
> mdadm: Cannot set device size/shape for /dev/md5: No space left on device
Yep.
The '--size' option refers to:
Amount (in Kibibytes) of space to use from each drive in
RAID1/4/5/6. This must be a multiple of the chunk size, and
must leave about 128Kb of space at the end of the drive for the
RAID superblock.
(from the man page).
So you were telling md to use the first 600GB of each device in the
array, and it told you there wasn't that much room.
If your array has N drives, you need to divide the target array size
by N-1 to find the target device size.
So if you have a 5 drive array, then you want
--size=157286400
NeilBrown
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