On 14/07/17 00:17, Ram Ramesh wrote:
I am trying to shring my mdadm underlying disks/partitions as a way of
reclaiming space after md shrink operation. Here is my md
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md0 : active raid6 sdb1[6] sdg1[11] sdd1[12] sdf1[8] sde1[9] sdc1[10]
12348030976 blocks super 1.2 level 6, 64k chunk, algorithm 2
[6/6] [UUUUUU]
bitmap: 2/23 pages [8KB], 65536KB chunk
unused devices: <none>
Here is my mdadm detail about /dev/sdb1
Avail Dev Size : 11720780943 (5588.90 GiB 6001.04 GB)
Array Size : 12348030976 (11776.00 GiB 12644.38 GB)
Used Dev Size : 6174015488 (2944.00 GiB 3161.10 GB)
I fail, remove and repartition /dev/sdb1 so that new partition table
looks like this. (No change to data obviously)
New partition table:
Number Start (sector) End (sector) Size Code Name
1 2048 6442452991 3.0 TiB FD00 Linux RAID
2 6442452992 11721045134 2.5 TiB FD00 Linux RAID
Since new /dev/sdb1 is significantly bigger than what mdadm says that it
is using, I thought I could simply re-add the drive. However, I get
sudo mdadm /dev/md0 --re-add /dev/sdb1
***mdadm: --re-add for /dev/sdb1 to /dev/md0 is not possible***
Why? What did I miss here? Is it possible to fix this so that I can
repartition other drives and -re-add them without having to go through
full rebuild after each change?
I researched as much as I could on the net and came up with nothing
except some one saying that mdadm keeps something at the end of the disk
regardless of what it says about "Used Dev Size." Is it possible to move
this info so that I could re-add?
I can't say why it won't re-add, but what's at the end of the disk is
the superblock - except it isn't at the end. The 0.9, or v1.0,
superblocks are at the end, but you've got a v1.2 superblock which is
stored at the start - to be precise, 4K in from the front of the partition.
Cheers,
Wol
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
