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

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

[Nikolay Kichukov]

-----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

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

[Mathias Burén]

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
>
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> --
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AFAIK growing raid0 is not possible.

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

[NeilBrown]

[-- 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-----
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> > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
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> > --
> > 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

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

[Nikolay Kichukov]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hello Neil,

Here goes the details. Once again, no valuable data, just curious what has gone wrong in that case:

dmesg output, first I stopped md2, then assembled it again to perform the grow.
http://pastebin.com/HkPVEKad

mdadm -E output:
http://pastebin.com/pJCjvrJE

The system runs GNU/Debian testing with latest updates from security-testing applied.
Kernel: 3.1.0-1-amd64
mdadm:  3.2.2-1

Let me know should you need any further information.

Cheers,
- -Nik

On 01/26/2012 12:57 PM, NeilBrown wrote:
> 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:
> 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
> 
- --
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>>
>>
>> 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
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Re: add another disk to existing raid 0, ie grow raid 0 possible?

[NeilBrown]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Thu, 26 Jan 2012 13:30:53 +0200 Nikolay Kichukov <hijacker@oldum.net>
wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hello Neil,
> 
> Here goes the details. Once again, no valuable data, just curious what has gone wrong in that case:
> 
> dmesg output, first I stopped md2, then assembled it again to perform the grow.
> http://pastebin.com/HkPVEKad

Hmmm... definitely looks sick.

> 
> mdadm -E output:
> http://pastebin.com/pJCjvrJE
> 
> The system runs GNU/Debian testing with latest updates from security-testing applied.
> Kernel: 3.1.0-1-amd64
> mdadm:  3.2.2-1

Those should be recent enough ... I guess I must have broken something.  This
will need more than a couple of minutes - I'll try to have a proper look next
week.

Thanks for the report,

NeilBrown



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

[Nikolay Kichukov]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,
sure, take your time. I am rebooting this kernel now and will setup the raid 0 from scratch with 3 disks/partitions.

Best,
- -Nik

On 01/26/2012 01:52 PM, NeilBrown wrote:
> On Thu, 26 Jan 2012 13:30:53 +0200 Nikolay Kichukov <hijacker@oldum.net>
> wrote:
> 
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
> 
>> Hello Neil,
> 
>> Here goes the details. Once again, no valuable data, just curious what has gone wrong in that case:
> 
>> dmesg output, first I stopped md2, then assembled it again to perform the grow.
>> http://pastebin.com/HkPVEKad
> 
> Hmmm... definitely looks sick.
> 
> 
>> mdadm -E output:
>> http://pastebin.com/pJCjvrJE
> 
>> The system runs GNU/Debian testing with latest updates from security-testing applied.
>> Kernel: 3.1.0-1-amd64
>> mdadm:  3.2.2-1
> 
> Those should be recent enough ... I guess I must have broken something.  This
> will need more than a couple of minutes - I'll try to have a proper look next
> week.
> 
> Thanks for the report,
> 
> NeilBrown
> 
> 
> 
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Re: add another disk to existing raid 0, ie grow raid 0 possible?

[NeilBrown]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Thu, 26 Jan 2012 13:30:53 +0200 Nikolay Kichukov <hijacker@oldum.net>
wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hello Neil,
> 
> Here goes the details. Once again, no valuable data, just curious what has gone wrong in that case:
> 
> dmesg output, first I stopped md2, then assembled it again to perform the grow.
> http://pastebin.com/HkPVEKad
> 
> mdadm -E output:
> http://pastebin.com/pJCjvrJE
> 
> The system runs GNU/Debian testing with latest updates from security-testing applied.
> Kernel: 3.1.0-1-amd64
> mdadm:  3.2.2-1
> 
> Let me know should you need any further information.

I've finally had a look at this and unfortunately cannot find the problem.
The main reason being that I cannot reproduce it.
I built the same kernel and mdadm and created a very similar array and
tried to grow it and it all went smoothly.

In your case it didn't start the reshape at all (reshape position was zero) so
something went wrong very early.

If you feel like trying to reproduce it again that might be helpful.
Then I would ask you to run the "mdadm --grow" command under 
    strace -o /tmp/foo -f mdadm --grow ....

and send me the /tmp/foo.  But I won't be surprised if you cannot reproduce.
Sad really.

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

[Nikolay Kichukov]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi Neil,
Do you think it will make sense to try to replicate using loop devices?

Cheers,
- -Nik

On 02/09/2012 05:50 AM, NeilBrown wrote:
> On Thu, 26 Jan 2012 13:30:53 +0200 Nikolay Kichukov <hijacker@oldum.net>
> wrote:
> 
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
> 
>> Hello Neil,
> 
>> Here goes the details. Once again, no valuable data, just curious what has gone wrong in that case:
> 
>> dmesg output, first I stopped md2, then assembled it again to perform the grow.
>> http://pastebin.com/HkPVEKad
> 
>> mdadm -E output:
>> http://pastebin.com/pJCjvrJE
> 
>> The system runs GNU/Debian testing with latest updates from security-testing applied.
>> Kernel: 3.1.0-1-amd64
>> mdadm:  3.2.2-1
> 
>> Let me know should you need any further information.
> 
> I've finally had a look at this and unfortunately cannot find the problem.
> The main reason being that I cannot reproduce it.
> I built the same kernel and mdadm and created a very similar array and
> tried to grow it and it all went smoothly.
> 
> In your case it didn't start the reshape at all (reshape position was zero) so
> something went wrong very early.
> 
> If you feel like trying to reproduce it again that might be helpful.
> Then I would ask you to run the "mdadm --grow" command under 
>     strace -o /tmp/foo -f mdadm --grow ....
> 
> and send me the /tmp/foo.  But I won't be surprised if you cannot reproduce.
> Sad really.
> 
> Thanks anyway,
> NeilBrown
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Re: add another disk to existing raid 0, ie grow raid 0 possible?

[NeilBrown]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Fri, 10 Feb 2012 16:10:09 +0200 Nikolay Kichukov <hijacker@oldum.net>
wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hi Neil,
> Do you think it will make sense to try to replicate using loop devices?

It certainly won't hurt.  It might not achieve anything though.
Give it a try ... it you manage to reproduce, let me know.

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

[Nikolay Kichukov]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hello Neil,
Here is the result, I think I managed to reproduce it as it has converted the raid0 to raid4.


so commands in sequence:

mdadm --verbose --create /dev/md/mdtest --level=0 --raid-devices=2 --metadata=1.2 /dev/loop0 /dev/loop1
mdadm: chunk size defaults to 512K
mdadm: array /dev/md/mdtest started.

strace -o /tmp/foo -f mdadm --grow /dev/md/mdtest --raid-devices=3 --add /dev/loop2
mdadm: level of /dev/md/mdtest changed to raid4
mdadm: /dev/loop2 not large enough to join array
mdadm: Need to backup 3072K of critical section..
mdadm: /dev/md/mdtest: Cannot grow - need a spare or backup-file to backup critical section
mdadm: aborting level change


The 3 devices are equal sizes, all 200MB in size:

- -rw-r--r--  1 root     root     209715200 Feb 14 11:28 raid_device1.loopback
- -rw-r--r--  1 root     root     209715200 Feb 14 11:28 raid_device2.loopback
- -rw-r--r--  1 root     root     209715200 Feb 14 11:17 raid_device3.loopback


Output of mdadm -E :

http://pastebin.com/WBhgP4L5

Contents of /tmp/foo:

http://pastebin.com/jcietEaa

Let me know if you need any more information to debug this.

Thanks,
- -Nik

On 02/13/2012 12:07 AM, NeilBrown wrote:
> On Fri, 10 Feb 2012 16:10:09 +0200 Nikolay Kichukov <hijacker@oldum.net>
> wrote:
> 
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
> 
>> Hi Neil,
>> Do you think it will make sense to try to replicate using loop devices?
> 
> It certainly won't hurt.  It might not achieve anything though.
> Give it a try ... it you manage to reproduce, let me know.
> 
> Thanks,
> NeilBrown
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Re: add another disk to existing raid 0, ie grow raid 0 possible?

[NeilBrown]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Tue, 14 Feb 2012 11:43:30 +0200 Nikolay Kichukov <hijacker@oldum.net>
wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hello Neil,
> Here is the result, I think I managed to reproduce it as it has converted the raid0 to raid4.
> 
> 
> so commands in sequence:
> 
> mdadm --verbose --create /dev/md/mdtest --level=0 --raid-devices=2 --metadata=1.2 /dev/loop0 /dev/loop1
> mdadm: chunk size defaults to 512K
> mdadm: array /dev/md/mdtest started.
> 
> strace -o /tmp/foo -f mdadm --grow /dev/md/mdtest --raid-devices=3 --add /dev/loop2
> mdadm: level of /dev/md/mdtest changed to raid4
> mdadm: /dev/loop2 not large enough to join array
> mdadm: Need to backup 3072K of critical section..
> mdadm: /dev/md/mdtest: Cannot grow - need a spare or backup-file to backup critical section
> mdadm: aborting level change
> 

I tried exactly that and it worked perfectly.
Maybe the bug has been fixed.
Please remind me exactly which versions of mdadm and linux you are using.

Thanks,
NeilBrown


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

[Nikolay Kichukov]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,
It really might be fixed in recent code, just for consistency:

dpkg -l | grep mdadm
ii  mdadm                                         3.2.3-2                          tool to administer Linux MD arrays
(software RAID)

uname -a
Linux hanna64 3.1.0-1-amd64 #1 SMP Tue Jan 10 05:01:58 UTC 2012 x86_64 GNU/Linux



Cheers,
- -Nik

On 02/16/2012 08:55 AM, NeilBrown wrote:
> On Tue, 14 Feb 2012 11:43:30 +0200 Nikolay Kichukov <hijacker@oldum.net>
> wrote:
> 
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
> 
>> Hello Neil,
>> Here is the result, I think I managed to reproduce it as it has converted the raid0 to raid4.
> 
> 
>> so commands in sequence:
> 
>> mdadm --verbose --create /dev/md/mdtest --level=0 --raid-devices=2 --metadata=1.2 /dev/loop0 /dev/loop1
>> mdadm: chunk size defaults to 512K
>> mdadm: array /dev/md/mdtest started.
> 
>> strace -o /tmp/foo -f mdadm --grow /dev/md/mdtest --raid-devices=3 --add /dev/loop2
>> mdadm: level of /dev/md/mdtest changed to raid4
>> mdadm: /dev/loop2 not large enough to join array
>> mdadm: Need to backup 3072K of critical section..
>> mdadm: /dev/md/mdtest: Cannot grow - need a spare or backup-file to backup critical section
>> mdadm: aborting level change
> 
> 
> I tried exactly that and it worked perfectly.
> Maybe the bug has been fixed.
> Please remind me exactly which versions of mdadm and linux you are using.
> 
> Thanks,
> NeilBrown
> 
> 
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Re: add another disk to existing raid 0, ie grow raid 0 possible?

[NeilBrown]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Thu, 16 Feb 2012 17:38:52 +0200 Nikolay Kichukov <hijacker@oldum.net>
wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hi,
> It really might be fixed in recent code, just for consistency:
> 
> dpkg -l | grep mdadm
> ii  mdadm                                         3.2.3-2                          tool to administer Linux MD arrays
> (software RAID)
> 
> uname -a
> Linux hanna64 3.1.0-1-amd64 #1 SMP Tue Jan 10 05:01:58 UTC 2012 x86_64 GNU/Linux
> 

Odd.. I cannot find any changes since then that would fix the problem.

The main problem is that mdadm decides that /dev/loop2 is too small.
The size that it wants it to be that it extracts from the array looks
correct.  I cannot see from the trace what size it thinks /dev/loop2 is,
but presumably it is the same as raid_device3.loopback, which is definitely
big enough.

As I said .. odd.

NeilBrown
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