On Wed, 12 Oct 2011 10:25:16 +0100 Michael Busby [off-list ref]
wrote:

Thanks, can i just double check the command with you

mdadm --create /dev/md0 --chunk=512 --metadata=1.0 --assume-clean
--level=5 --raid-devices=4 /dev/sde /dev/sdc /dev/sdd /dev/sdb

Correct.  Of course you have to
   mdadm --stop /dev/md0
first, but you knew that.

NeilBrown

On 12 October 2011 05:10, NeilBrown [off-list ref] wrote:

quoted

On Mon, 10 Oct 2011 22:47:58 +0100 Michael Busby [off-list ref]
wrote:

quoted

I have a quick question i remember reading somewhere about not using
metadata version 0.9 with drives larger than 2tb,

quoted

at the moment i have the following

root@BlueBolt:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid5 sdd[2] sde[0] sdb[3] sdc[1]
      5860543488 blocks level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
      bitmap: 2/15 pages [8KB], 65536KB chunk
unused devices: <none>
root@BlueBolt:~# mdadm --detail /dev/md0
/dev/md0:
        Version : 0.90
  Creation Time : Mon Jul  4 15:08:38 2011
     Raid Level : raid5
     Array Size : 5860543488 (5589.05 GiB 6001.20 GB)
  Used Dev Size : 1953514496 (1863.02 GiB 2000.40 GB)
   Raid Devices : 4
  Total Devices : 4
Preferred Minor : 0
    Persistence : Superblock is persistent
  Intent Bitmap : Internal
    Update Time : Mon Oct 10 22:44:11 2011
          State : active
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0
         Layout : left-symmetric
     Chunk Size : 512K
           UUID : ddab6c38:dee3ead0:95ba4558:1c9a49ed (local to host BlueBolt)
         Events : 0.2836102
    Number   Major   Minor   RaidDevice State
       0       8       64        0      active sync   /dev/sde
       1       8       32        1      active sync   /dev/sdc
       2       8       48        2      active sync   /dev/sdd
       3       8       16        3      active sync   /dev/sdb
which as you can see if using 0.90, i am looking at replacing all the 2tb drives with 3tb versions, would i need to update the metadata version? if so how can i go about this?

With a really recent kernel (3.1) and recent mdadm (also not released yet),
0.90 can go up to 4TB (it has 32 bits to count kilobytes with).

Alternately you need to convert to 1.0 metadata.

Currently the only way to do this is to 'create' the array again.
Be sure to specified the same chunk size, the right metadata, the name level
and number of disks, and the correct disks in the correct order.
An use "--assume-clean".  Then check your data is still consistent.
With --assume-clean and a read-only mount, no data will actually be changed,
only metadata.

NeilBrown