On Wed, 12 Oct 2011 10:25:16 +0100 Michael Busby <michael.a.busby@gmail.com>
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 <neilb@suse.de> wrote:
> > On Mon, 10 Oct 2011 22:47:58 +0100 Michael Busby <michael.a.busby@gmail.com>
> > wrote:
> >
> >> I have a quick question i remember reading somewhere about not using
> >> metadata version 0.9 with drives larger than 2tb,
> >> > 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
> >
> >