IBM TotalStorage DS300 Best Practices Manual page 168

The difference between this two hotspare types are the arrays for which a
hotspare will be used. Assigned hotspare drives will only be used for the array
they are assigned for. Global hotspare drives will be used for all critical arrays.
When both types of hotspares are configured, the assigned hotspares will be
used first and than the global hotspares.
Multiple hotspares of either type can be assigned.
Note: Select a global hotspare drive that has the same capacity as the largest
drives installed in the controller. Not all arrays and logical drives will be
protected when drives with a smaller size are defined as hotspare. When
small and large capacity drives are defined as global hotspares, the largest
one is always selected first to rebuild an array with a disabled drive.
Create assigned hotspare drive
To create an assigned hotspare follow the steps below:
1. Right-click drive 14 → Create assigned hot-spare drive for →
Spanned-array-1.
array manage
Spanned-array-1
spare add 3584
Figure 4-120 SRM - Create array specific hotspare
2. The selected dive 14 will get a small plus to symbolize that this drive will be
used as a hotspare drive. Select the drive (by clicking) to see to which array it
was assigned. The array and all logical drive will be highlighted as well.
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IBM TotalStorage DS300 and DS400 Best Practices Guide