mdadm -E won't examine loop back device, works ok on source disk

Discussion:

Veedar Hokstadt

2012-04-22 21:00:04 UTC

Consider a SATA drive /dev/sdb which is a member of an imsm RAID0 array...

% sum /dev/sdb
25645 156290904

The drive was imaged to a file without error and mounted as a loopback device...

% sum /dev/loop2
25645 156290904

The checksums match as expected. But I can not examine the loopback I get....

% mdadm -E -v /dev/loop2
mdadm: No md superblock detected on /dev/loop2.

But I can examine the physical source drive /dev/sdb...

% mdadm -E -v /dev/sdb
/dev/sdb:
Magic : Intel Raid ISM Cfg Sig.
Version : 1.0.00
Orig Family : e92a11d9
Family : e92a11d9
Generation : 00001608
UUID : 25137636:2ff64e75:10ae5444:4e8f609b
Checksum : e1237b20 correct
MPB Sectors : 1
Disks : 2
RAID Devices : 1

Disk01 Serial : 8068C3QVT
State : active
Id : 00010000
Usable Size : 312577294 (149.05 GiB 160.04 GB)

[Volume0]:
UUID : 72acd5fa:35c5a901:995af79b:83a29de1
RAID Level : 0
Members : 2
This Slot : 1
Array Size : 625154048 (298.10 GiB 320.08 GB)
Per Dev Size : 312577283 (149.05 GiB 160.04 GB)
Sector Offset : 0
Num Stripes : 1221004
Chunk Size : 128 KiB
Reserved : 0
Migrate State : idle
Map State : normal
Dirty State : clean

Disk00 Serial : 809BC541T
State : active failed
Id : 00000000
Usable Size : 312577294 (149.05 GiB 160.04 GB)

I'm trying to recover data from a failed RAID0.
I can successfully reassemble the RAID0 from the image files using
other proprietary recovery software.
But I would like to get it working with mdadm if at all possible.
Any ideas?

Regards,
V
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NeilBrown

2012-04-22 21:58:16 UTC

Permalink

Post by Veedar Hokstadt
Consider a SATA drive /dev/sdb which is a member of an imsm RAID0 array...
% sum /dev/sdb
25645 156290904
The drive was imaged to a file without error and mounted as a loopback device...
% sum /dev/loop2
25645 156290904
The checksums match as expected. But I can not examine the loopback I get....
% mdadm -E -v /dev/loop2
mdadm: No md superblock detected on /dev/loop2.
But I can examine the physical source drive /dev/sdb...
% mdadm -E -v /dev/sdb
Magic : Intel Raid ISM Cfg Sig.
Version : 1.0.00
Orig Family : e92a11d9
Family : e92a11d9
Generation : 00001608
UUID : 25137636:2ff64e75:10ae5444:4e8f609b
Checksum : e1237b20 correct
MPB Sectors : 1
Disks : 2
RAID Devices : 1
Disk01 Serial : 8068C3QVT
State : active
Id : 00010000
Usable Size : 312577294 (149.05 GiB 160.04 GB)
UUID : 72acd5fa:35c5a901:995af79b:83a29de1
RAID Level : 0
Members : 2
This Slot : 1
Array Size : 625154048 (298.10 GiB 320.08 GB)
Per Dev Size : 312577283 (149.05 GiB 160.04 GB)
Sector Offset : 0
Num Stripes : 1221004
Chunk Size : 128 KiB
Reserved : 0
Migrate State : idle
Map State : normal
Dirty State : clean
Disk00 Serial : 809BC541T
State : active failed
Id : 00000000
Usable Size : 312577294 (149.05 GiB 160.04 GB)
I'm trying to recover data from a failed RAID0.
I can successfully reassemble the RAID0 from the image files using
other proprietary recovery software.
But I would like to get it working with mdadm if at all possible.
Any ideas?

Try setting IMSM_NO_PLATFORM in the environment:

IMSM_NO_PLATFORM=1 mdadm -E -v /dev/loop2

or

export IMSM_NO_PLATFORM=1
mdadm -E -v /dev/loop2

I think this is fixed in more recent mdadm. You still need IMSM_NO_PLATFORM
to create or assemble an array, but not just to look at it.

NeilBrown

Veedar Hokstadt

2012-04-23 04:46:16 UTC

Permalink

Thanks for your reply but setting IMSM_NO_PLATFORM seems to have no eff=
ect...

% export IMSM_NO_PLATFORM=3D1
% echo $IMSM_NO_PLATFORM
1

% mdadm -V
mdadm - v3.2.3 - 23rd December 2011

% mdadm -E -v /dev/loop2
mdadm: No md superblock detected on /dev/loop2.

% export IMSM_NO_PLATFORM=3D""
% echo $IMSM_NO_PLATFORM

% mdadm -E -v /dev/loop2
mdadm: No md superblock detected on /dev/loop2.

And trying to assemble fails...
export IMSM_NO_PLATFORM=3D1
% mdadm --assemble /dev/md0 /dev/loop1 /dev/loop2
mdadm: Cannot assemble mbr metadata on /dev/loop1
mdadm: /dev/loop1 has no superblock - assembly aborted

Regards,
V

Consider a SATA drive /dev/sdb which is a member of an imsm RAID0 ar=

ray...

% sum /dev/sdb
25645 156290904
The drive was imaged to a file without error and mounted as a loopba=

ck device...

% sum /dev/loop2
25645 156290904
The checksums match as expected. But I can not examine the loopback =

I get....

% mdadm =A0-E -v /dev/loop2
mdadm: No md superblock detected on /dev/loop2.
But I can examine the physical source drive /dev/sdb...
% mdadm =A0-E -v /dev/sdb
=A0 =A0 =A0 =A0 =A0 Magic : Intel Raid ISM Cfg Sig.
=A0 =A0 =A0 =A0 Version : 1.0.00
=A0 =A0 Orig Family : e92a11d9
=A0 =A0 =A0 =A0 =A0Family : e92a11d9
=A0 =A0 =A0Generation : 00001608
=A0 =A0 =A0 =A0 =A0 =A0UUID : 25137636:2ff64e75:10ae5444:4e8f609b
=A0 =A0 =A0 =A0Checksum : e1237b20 correct
=A0 =A0 MPB Sectors : 1
=A0 =A0 =A0 =A0 =A0 Disks : 2
=A0 =A0RAID Devices : 1
=A0 Disk01 Serial : 8068C3QVT
=A0 =A0 =A0 =A0 =A0 State : active
=A0 =A0 =A0 =A0 =A0 =A0 =A0Id : 00010000
=A0 =A0 Usable Size : 312577294 (149.05 GiB 160.04 GB)
=A0 =A0 =A0 =A0 =A0 =A0UUID : 72acd5fa:35c5a901:995af79b:83a29de1
=A0 =A0 =A0RAID Level : 0
=A0 =A0 =A0 =A0 Members : 2
=A0 =A0 =A0 This Slot : 1
=A0 =A0 =A0Array Size : 625154048 (298.10 GiB 320.08 GB)
=A0 =A0Per Dev Size : 312577283 (149.05 GiB 160.04 GB)
=A0 Sector Offset : 0
=A0 =A0 Num Stripes : 1221004
=A0 =A0 =A0Chunk Size : 128 KiB
=A0 =A0 =A0 =A0Reserved : 0
=A0 Migrate State : idle
=A0 =A0 =A0 Map State : normal
=A0 =A0 Dirty State : clean
=A0 Disk00 Serial : 809BC541T
=A0 =A0 =A0 =A0 =A0 State : active failed
=A0 =A0 =A0 =A0 =A0 =A0 =A0Id : 00000000
=A0 =A0 Usable Size : 312577294 (149.05 GiB 160.04 GB)
I'm trying to recover data from a failed RAID0.
I can successfully reassemble the RAID0 from the image files using
other proprietary recovery software.
But I would like to get it working with mdadm if at all possible.
Any ideas?

=A0IMSM_NO_PLATFORM=3D1 mdadm -E -v /dev/loop2
or
=A0export IMSM_NO_PLATFORM=3D1
=A0mdadm -E -v /dev/loop2
I think this is fixed in more recent mdadm. =A0You still need IMSM_NO=

_PLATFORM

to create or assemble an array, but not just to look at it.
NeilBrown

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NeilBrown

2012-04-23 05:04:54 UTC

Permalink

Thanks for your reply but setting IMSM_NO_PLATFORM seems to have no effect...
% export IMSM_NO_PLATFORM=1
% echo $IMSM_NO_PLATFORM
1
% mdadm -V
mdadm - v3.2.3 - 23rd December 2011
% mdadm -E -v /dev/loop2
mdadm: No md superblock detected on /dev/loop2.

Hmmmm....

Looks like you need
IMSM_DEVNAME_AS_SERIAL=1
as well. IMSM like to know the 'serial number' of each device and gets
confused when there isn't once ... and loop doesn't have serial numbers.

I should see if I can fix that.

Thanks
NeilBrown

% export IMSM_NO_PLATFORM=""
% echo $IMSM_NO_PLATFORM
% mdadm -E -v /dev/loop2
mdadm: No md superblock detected on /dev/loop2.
And trying to assemble fails...
export IMSM_NO_PLATFORM=1
% mdadm --assemble /dev/md0 /dev/loop1 /dev/loop2
mdadm: Cannot assemble mbr metadata on /dev/loop1
mdadm: /dev/loop1 has no superblock - assembly aborted
Regards,
V

IMSM_NO_PLATFORM=1 mdadm -E -v /dev/loop2
or
export IMSM_NO_PLATFORM=1
mdadm -E -v /dev/loop2
I think this is fixed in more recent mdadm. You still need IMSM_NO_PLATFORM
to create or assemble an array, but not just to look at it.
NeilBrown

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To unsubscribe from this list: send the line "unsubscribe linux-raid" in
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