Dell POWERVAULT MD3600F - Manual (Page 239)

Management: Firmware Downloads 239
Media Errors and Unreadable Sectors
If the RAID controller detects a media error while accessing data from a
physical disk that is a member of a disk group with a redundant RAID level
(RAID 1, RAID 5 or RAID 10), the controller tries to recover the data from
peer disks in the disk group and uses recovered data to correct the error. If the
controller encounters an error while accessing a peer disk, it is unable to
recover the data and affected sectors are added to the unreadable sector log
maintained by the controller. Other conditions under which sectors are added
to the unreadable sector log include:
• A media error is encountered when trying to access a physical disk that is a
member of a non-redundant disk group (RAID 0 or degraded RAID 1,
RAID 5 or RAID 10).
• An error is encountered on source disks during rebuild.
NOTE: Data on an unreadable sector is no longer accessible.
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