Identify failed disk in Linux RAID Post: 302562352

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Top Forums UNIX for Advanced & Expert Users Identify failed disk in Linux RAID Post 302562352 by Loic Domaigne on Thursday 6th of October 2011 03:04:10 PM

10-06-2011

Registered User

Identify failed disk in Linux RAID

Good Evening,

2 years ago, I set up an Ubuntu file-server for a friend, who is a photograph amateur. Basically, the server offers a software RAID-5 that can be accessed remotely from a MAC. Unfortunately, I didn't labeled the hard drives (i.e. which physical drive corresponds to the /dev/sdX device).

Now a drive has failed, and the RAID-5 is at risk. I needed to find out which physical drive we have to replace, before we can rebuild the array. I have summed up below the procedure I'd follow. It would be great if some Linux software RAID connaisseur could review it. The more eyeballs, the better; and beside Linux RAID are quite new land for me.

1. stop raid system
# umount /dev/md1
# mdadm -S /dev/md1

2. Unplug one by one the hard drives. Looks in dmesg failure events for /dev/sdX. That way the mapping between the physical disk and the device /dev/sdX is step-by-step revealed.

3. Replace the failed disk, and partition it accordingly to what is expected.

4. Rebuild the mirror with the new disk
- get UUID with mdadm -query
- assemble array with that new disk: mdadm --assemble /dev/md -u XXX
- update /etc/mdadm.conf: mdadm --detail --scan >> /etc/mdadm.conf

You find below detailed information about the server set-up.

TIA,
Lo�c

The setup:

Ubuntu server, 6 SATA Hard drives /dev/sda ... /dev/sdf

Each Drives (X=a..f) are partitioned as followed:
/sdX1 type Linux Partition
/sdX2 type swap
/sdX3 type extended
/sdX5 type RAID

The server has 2 software Raids:
/dev/md0 RAID1 /sda1 and /sdb1
/dev/md1 RAID5 /sda5, /sdb5, /sdc5, /sdd5, /sde5, /sdf5

The OS is located on /dev/md0, only application data are located on /dev/md1

The Failure:

A Fail event had been detected on md device /dev/md1.
It could be related to component device /dev/sdd5.
The /proc/mdstat file currently contains the following:

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid5 sde5[4] sdc5[2] sdd5[6](F) sdf5[5] sdb5[1] sda5[0]
9636429120 blocks level 5, 64k chunk, algorithm 2 [6/5] [UUU_UU]

md0 : active raid1 sdb1[1] sda1[0]
20506816 blocks [2/2] [UU]

unused devices: <none>

Loic Domaigne

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vxr5check

vxr5check(1M)															     vxr5check(1M)

NAME

       vxr5check - verify RAID-5 volume parity

SYNOPSIS

       /etc/vx/bin/vxr5check [-i | -v] [-g diskgroup] volume

DESCRIPTION

       The vxr5check utility compares the parity of each stripe of a RAID-5 volume specified by volume.  vxr5check reads the data for each stripe,
       generates the parity for this stripe, and compares this parity with the existing parity.

       vxr5check can be run against the entire RAID-5 volume, or incrementally on RAID-5 stripe boundaries, by specifying the -i option.

OPTIONS

       -g diskgroup
		 Specifies the Veritas Volume Manager (VxVM) disk group name for the RAID-5 volume name for verification.  If this option  is  not
		 specified, the default disk group is determined using the rules given in the vxdg(1M) manual page.

       -i	 Verifies the RAID-5 volume incrementally per stripes.	If a parity mismatch is found, that stripe location is displayed.

       -v	 Verbose output for the incremental vxr5check verification.  The verbose option outputs each stripe number that is being verified.

OUTPUT FORMAT

       In  verbose  mode and incremental mode, summary reports for each stripe of the RAID-5 volume are printed in output records.  If an error is
       returned for a stripe, then an error message and stripe number are displayed.  In non-verbose mode, if an error is returned, an error  mes-
       sage is displayed.

       If a parity mismatch error is determined on a stripe, vxr5check exits on that stripe and does not continue for the remaining stripes in the
       RAID-5 volume.

FILES

       /usr/lib/vxvm/bin/vxr5vrfy    The utility that vxr5check calls to perform RAID-5 parity verification operations for  the  specified  RAID-5
				     volume.

EXIT CODES

       The  vxr5check  utility exits with a non-zero status if the attempted operation fails.  A non-zero exit code is not a complete indicator of
       the problems encountered, but rather denotes the first condition that prevented further execution of the utility.

       See vxintro(1M) for a list of standard exit codes.

NOTES

       Do not run vxr5check on a volume that is in degraded mode.

SEE ALSO

       vxevac(1M), vxintro(1M), vxmend(1M), vxvol(1M)

VxVM 5.0.31.1							    24 Mar 2008 						     vxr5check(1M)