Hello Adam,
Cetnerowski, Adam wrote:
The problem stems from dmraid not supporting loop devices. You can
change this behavior by either modifying the device names or the
function that parses the device names. Either way please take a look at
interested() in lib/device/scan.c
thank you very much for the hint, but I was not able to make it work. My
initial attempt was to just create a new hard link in /dev for the loop
device:
ln /dev/loop0 /dev/hdi
ln /dev/loop1 /dev/hdj
but I found out that dmraid is scanning the directory /sys/block to find
block devices and in there I cannot create new files/hard links.
After modifying the source of dmraid to accept loop devices it still
does not work, because in the get_device_serial() function dmraid uses
ioctls to get the serial numbers of the scanned devices and the loop
devices do not have a serial number.
I see that get_dm_test_serial() gets the serial number from a file, but
I still have to find out how this works. I've read in the document "
dmraid - device-mapper RAID tool
Supporting ATARAID devices via the generic Linux device-mapper
Heinz Mauelshagen
Red Hat Cluster and Storage Development
"
in section 3.4 Testbed that it should be possible to use this testbed
functionality for what I want, but I am not certain on what exactly I
have to do?
I still cannot understand why even with working directly with dmsetup I
cannot setup a working device map.
I think for the short term I will just create backups of the mapped
devcies, e.g.:
/dev/mapper/isw_bjebjjjbd_RAID_Volume04
But for the future perhaps it would be possible to add the functionality
to dmraid to be able to map disk images like I intended to do, e.g. if
you specify on the commandline the loop device nodes:
dmraid -r /dev/loop0 /dev/loop1
I think it is really serious that it is not possible to take the disk
images in case of a disk failure and work with the disk images in order
to rescue as much data as possible. I've found the article:
http://robmeerman.co.uk/unix/medley?s=sata
"Rescuing a RAID-0 FAKE-RAID Array"
but he worked directly on the disks. I think there is really a shortage
of information about how to rescue data from failing ataraid devices.
Thank you very much for your help,
--
Christian Schuhegger
http://www.el-chef.de/
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