Server Administrator Storage Management 8.3 User’s Guide

Considerations For Hot Spares On PERC 6/E And PERC 6/I Controllers

On the PERC 6/E and PERC 6/I controllers, assigning a hot spare is equivalent to assigning a physical disk to replace another physical disk if it fails. If more than one redundant virtual disk resides on the physical disk, then all redundant portions of the physical disk are rebuilt.

NOTE: When rebuilding a physical disk delete any non-redundant virtual disks (such as RAID 0) that reside on the physical disk before rebuilding the physical disk.

NOTE: The order of the controllers displayed on Storage Management may differ with the order of the controllers displayed in the Human Interface (HII) and PERC Option ROM. The order of the controllers does not cause any limitation.

When creating a virtual disk, the physical disks included in the virtual disk can vary in size. Ensure that the hot spare must be the same size (or greater) as the smallest physical disk included in the virtual disk when assigning a hot spare to a RAID 1 or 5 virtual disk.

When you use a PERC 6/E and PERC 6/I controller, you can assign physical disks of different sizes to a virtual disk. When a virtual disk is assigned to a physical disk, any portion of the physical disk that is unused by the virtual disk becomes unusable. Therefore, the data on the unused portion of the physical disk is not rebuilt. A redundant virtual disk is also either striped or mirrored in equal portions across its member physical disks. The amount of data requiring a rebuild is therefore not greater than the smallest physical disk.

A RAID 10 or 50 virtual disk may include spans that have physical disks of different sizes. In this case, identify the span that has a low capacity physical disk. The hot spare should be large enough to rebuild this physical disk. For example, if one span has three physical disks that are 60MB, 60MB and 40MB and another span has physical disks that are 60MB, 60MB, and 50MB, then the hot spare must be 50MB or larger.

A dedicated hot spare can only be assigned to the set of virtual disks that share the same physical disks. A global hot spare is assigned to all redundant virtual disks on the controller. A global hot spare must be the same size (or greater) as the smallest physical disk included in any virtual disk on the controller.

After you have assigned a global hot spare, any new virtual disks created on the controller are not protected by the hot spare in either of the following circumstances:

• The controller is a SAS controller and the disk size is larger than the global hot spare.

In this case, you can unassign the global hot spare after creating a new virtual disk and then assign a new and larger hot spare to cover all redundant virtual disks on the controller. To determine whether the controller is using SAS technology, see RAID Controller Technology: SATA and SAS.