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

[NeilBrown <neilb@suse.de>]

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On Mon, 23 Apr 2012 00:46:16 -0400 Veedar Hokstadt <veedar@gmail.com> wrote:

> 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
> 
> On Sun, Apr 22, 2012 at 5:58 PM, NeilBrown <neilb@suse.de> wrote:
> > On Sun, 22 Apr 2012 17:00:04 -0400 Veedar Hokstadt <veedar@gmail.com> wrote:
> >
> >> 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?
> >>
> >
> > 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
> >
> >
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