Bad Blocks in IDE software Raid 1
Hello All
I have had a number of cases with disk's reporting as "failed" on
systems with IDE drives in software RAID 1 configuration.
I suppose the good news is you can change the drive with minimal
downtime and no loss of data. But some of my customers are
querying the apparent high failure rate.
As far as I know, with modern IDE drives the formated drive includes
spare blocks and the drive firmware will automatically re-map the drive
to replace bad blocks with ones from the spare space. This all
happens transparently without any feedback to the system log files.
Can somebody confirm that the above is true?
This would imply that bad blocks on one drive in an array are mapped
out by the firmware, until a point is reached where there are no spare
blocks on that drive. Further bad blocks would result in disk errors and
the drive would be "failed" out of the array.
The ext2 file system also handles mapping out of bad blocks. These
can be detected during the initial formating of the drive, or during
subsequent fsck runs.
Can somebody confirm that this is true?
Can ext2 file systems actively map out bad blocks during normal
operation?
Finally, if an ext2 filesystem is mounted on a Linux software raid1
device, and a file system error occurs, will a portion of that device be
mapped out as a bad block, or will one of the drives be "failed" out of
the array?
If ext2 maps out a bad block, I assume the same block on both the
good and bad drives gets mapped out.
If one of the drives is "failed" it would explain why the failure rate on
raid drives seems higher than that in single drive machines. ie Raid
fails the drive, while in a single drive machine ext2 caries on, hiding
the problem from the end user who is not watching the log files.
All input would be appreciated.
Thanks
Ian
---------------------------------------------------------------------
Ian Forbes ZSD
http://www.zsd.co.za
Office: +27 21 683-1388 Fax: +27 21 674-1106
Snail Mail: P.O. Box 46827, Glosderry, 7702, South Africa
---------------------------------------------------------------------
Reply to: