Server Administrator Storage Management 8.2 User’s Guide

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Managing Virtual Disk Bad Block Management

Virtual disk bad blocks are bad blocks on one or more member physical disks. The read operation on the virtual disks having bad blocks may fail.

Storage Management generates a critical alert (2387) to notify you of the bad blocks on the virtual disk.

Virtual disk bad blocks are discovered when the controller performs any operation that requires scanning the disk. Examples of operations that may result in this alert are:

Consistency check
Rebuild
Virtual disk format
I/O
Patrol Read

Recovering a physical disk bad block depends on the RAID level and state of the virtual disk. If a virtual disk is redundant, the controller can recover a bad block on a physical disk. If a virtual disk is not redundant, then the physical disk bad block results in a virtual disk bad block.

The following table describes some of the possible scenarios that may/may not result in virtual disk bad blocks:

Table 1. Sample Scenarios For Virtual Disk Bad Blocks
RAID Level Virtual Disk	State	Scenario	Result
RAID 0	Degraded	One bad block on a physical disk.	The controller cannot regenerate data from the peer disks as there is no redundancy. This results in a virtual disk bad block.
RAID 5	Ready	One bad block on a physical disk.	The controller regenerates data from the peer disks and sends a Write to the bad block. The disk then remaps the Logical Block Addressing (LBA) to another physical location. The problem is resolved.
RAID 5	Degraded	One bad block on a physical disk.	The controller cannot regenerate data from the peer disks because one drive is missing. This results in a virtual disk bad block.
RAID 5	Ready	One bad block on two physical disks at the same location.	The controller cannot regenerate data from the peer disks. This results in a virtual disk bad block.
RAID 6	Partially degraded (one failed/missing physical disk)	One bad block on a physical disk.	The controller regenerates data from the peer disks and sends a Write to the bad block. The disk then remaps the LBA to another physical location. The problem is resolved.
RAID 6	Degraded (two failed/missing physical disks)	One bad block on a physical disk.	The controller cannot regenerate data from the peer disks. This results in a virtual disk bad block.
RAID 6	Ready	One bad block on a physical disk.	The controller regenerates data from peer disks and sends a Write to the bad block. The disk then remaps the Logical Block Addressing (LBA) to another physical location. The problem is resolved.