Re: add another disk to existing raid 0, ie grow raid 0 possible?

[NeilBrown <neilb@suse.de>]

[-- Attachment #1: Type: text/plain, Size: 3338 bytes --]

On Thu, 26 Jan 2012 10:47:14 +0000 Mathias Burén <mathias.buren@gmail.com>
wrote:

> On 26 January 2012 10:26, Nikolay Kichukov <hijacker@oldum.net> wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > Hi all,
> >
> > I tried to expand md block device raid level 0 ( /dev/md2 ) by adding another partition to it.
> >
> > Here are the steps:
> >
> > mdadm --assemble /dev/md2
> > mdadm: /dev/md2 has been started with 2 drives.
> > hanna64:~# mdadm --grow /dev/md2 --raid-devices=3 --add /dev/sdc2
> > mdadm: level of /dev/md2 changed to raid4
> > mdadm: added /dev/sdc2
> > mdadm: Need to backup 3072K of critical section..
> >
> >
> > Now fdisk -l cannot complete, just goes to D state.
> >
> > Disks layout before the grow attempt:
> >
> > ARRAY /dev/md2 metadata=1.2 name=hanna64:2 UUID=4840f7f0:71b5f4a0:c4d8a42c:0b43b5fb
> >
> > /dev/sda2: UUID="4840f7f0-71b5-f4a0-c4d8-a42c0b43b5fb" TYPE="linux_raid_member" LABEL="hanna64:2"
> > UUID_SUB="cf97412f-269a-f3e8-fde2-8ca3bf42a349"
> > /dev/sdb2: UUID="4840f7f0-71b5-f4a0-c4d8-a42c0b43b5fb" TYPE="linux_raid_member" LABEL="hanna64:2"
> > UUID_SUB="9aee2d4c-6deb-911a-d790-cbd12f6c671c"
> >
> > md2 : active raid0 sda2[0] sdb2[1]
> >      15628288 blocks super 1.2 512k chunks
> >
> >
> > Disk /dev/md2: 16.0 GB, 16003366912 bytes
> > 2 heads, 4 sectors/track, 3907072 cylinders, total 31256576 sectors
> > Units = sectors of 1 * 512 = 512 bytes
> > Sector size (logical/physical): 512 bytes / 512 bytes
> > I/O size (minimum/optimal): 524288 bytes / 1048576 bytes
> > Disk identifier: 0x7b88c100
> >
> > Disk /dev/md2 doesn't contain a valid partition table
> >
> >
> > This array was used as swap, so no valuable information is stored there anyways. Let me know what has gone wrong and
> > what I typed wrong assuming the grow command will just add /dev/sdc2 to the existing array and make it larger with the
> > size of /dev/sdc2.
> >
> > Thank you,
> > - -Nikolay Kichukov
> >
> > -----BEGIN PGP SIGNATURE-----
> > Version: GnuPG v1.4.11 (GNU/Linux)
> > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
> >
> > iQEcBAEBAgAGBQJPISpZAAoJEDFLYVOGGjgXS4IIAIDdhB1lInCO9jpb9eQRyj8x
> > QQYl7B+t0pud/mBuML5T2eTou/qtLhp4Mdv0ZoiwJ7NIuouXuR1wOAbe7/LDkKwB
> > ku1iLjLpnqLtQZnctYV598cjH3q2mzb8zi7bOoD3FTGRN/DmyNik0WflsLA04TBc
> > 0ohR4KoQIA/j95CvhNrMhZ2tyUis8VmhN+aBzdCnm90gNE8fLJKpUsB1hKahocit
> > wSUg9ab/C2wDHTBp5mq1AJModgClCKMCUgf7Z4A1f2zP6NPy1xmoP88emGLUSo/b
> > NEMwNTqKjzKcxo67kl0xUGnp8kxVfCLGfjDQHUUFwMT1F9g/PWkgBD0CXmfBSbk=
> > =g/v/
> > -----END PGP SIGNATURE-----
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> 
> AFAIK growing raid0 is not possible.

Seems an odd thing to say, given that when OP demonstrated that mdadm
didn't complain, but went as far as converting the array to RAID4 so it could
perform a reshape.....

It wasn't possible once, but times change.

To know what went wrong I would need lots more details.
Start with the output of 'dmesg' - or equivalent from logs
(e.g. /var/log/kern.log or /var/log/messages).

Then "mdadm -E" output of each device in the array.

NeilBrown

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]