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Solution to the failure of Lun

Publication Date:  2012-09-18 Views:  39 Downloads:  0
Issue Description
The host failed to IO interfaces of the LUN, and the LUN was lost after disk scaning; Logging in the management interface of S2600 ISM, the label of the failure of LUN was found in logical view. As is displayed below:

Check the alarm information in ISM interface, and some failure and bad sectors were found in the members of the RAID group, which was displayed in the following figure, that failure in the harddisk (0,4) and bad sectors in the harddisk (0,5).  
Alarm Information
None
Handling Process
The RAID group was set degradation after one of its members lost efficacy. Before its recovery, if the IO of another member had bad sector, the system would set the LUN where the bad sector was failure while there was no influence to other LUN.
Handing Process
1. If there is a unused hot spare disk in system, change its type into spare, avoiding the system to start reconstruction automatically in step 3.
2. Recover all the member disks which have bad sectors one by one(maybe some), in this example, there was only one disk(0,5) which has bad sector,
a. Collect the smart information of the disks which have bad sectors;

b. Check the smart information, find the Pending Sector Table Entries of the disks, and ensure the LBA of bad sectors;

In this example, the LBA of the bad sector is 0x00002710.
c. Recover all the bad sectors with the disktool;
 
d. Back to step a till the record of Pending Sector Table Entries in disks is empty.
3. If the first disk which lost efficacy has associated with a hot spare disk, pull out the hot spare disk first to set the RAID group degradation, then use the command “revive lun<LunID>” to set the LUN which lost efficacy normal;

4. Replace the disk which lost efficacy, if so, swap the disk manually, and the system will start reconstruction automatically;
5. After the reconstruction is done, check the state of LUN and RAID are normal or not, recover the hot spare of the system;
6. Scan LUN in the host again, check the file system and recover the service after the LUN which lost efficacy was found.
Root Cause
The RAID group was set degradation after one of its members lost efficacy. Before its recovery, if the IO of another member had bad sector, the system would set the LUN where the bad sector was failure while there was no influence to other LUN.
Suggestions
Storage arrays are read and written all the time, it is normal to have bad sectors in the disks. It is suggested that upgrade to vision with I/O bad sector management of the array or the lasted vision in the client’s field.

END