Re: Raid5 to another raid level??

[Michael Busby <michael.a.busby@gmail.com>]

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


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
>
>
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