HP P3410A HP NetRAID 1M/2M Installation & Configuration - Page 20

Hot Spares, Logical Drives

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Chapter 2 RAID Overview Arrays can combine disk drives that are all on one channel of an HP NetRAID-1M or 2M adapter, or they can combine disk drives from both channels of an HP NetRAID-2M adapter. However, all the disk drives in an array must be connected to a single NetRAID adapter. Using internal connectors, this means that the maximum number of disk drives in an array is 6 (HP NetRAID1M) or 12 (HP NetRAID-2M). Using external connectors, the maximum number of disk drives in an array is 12 (HP NetRAID-1M) or 24 (HP NetRAID-2M). Hot Spares A hot spare is a powered-on, stand-by disk drive that is ready for use should another disk drive fail. When a disk fails, the HP NetRAID adapter's firmware can automatically rebuild the data from the failed disk onto the hot spare. The system administrator can then replace the failed disk and designate a new hot spare disk. Until a rebuild occurs, a hot spare does not contain user data. There are two types of hot spares: • A global hot spare is used if a disk in any array on the adapter fails. • A dedicated hot spare is reserved for use by a single array. Logical Drives The term "logical drive" refers to a virtual drive that is assigned some portion of the total capacity of an array. For example, if you have an array of disk drives with a total capacity of 80 GB, you can create a logical drive with a total capacity of 20-GB within that array. Logical drives can take three forms: • A logical drive can use all of the storage capacity of one array. In Figure 2-3, Logical Drive LD0 uses all storage capacity in Array A0. • A logical drive can use less than the available storage capacity of one array. In Figure 2-3, Logical Drive LD1 occupies only a part of Array A1. • A logical drive can span arrays by spreading across up to eight different arrays. In Figure 2-3, Logical Drive LD2 spans Arrays A1 and A2. In Figure 2-3, there are nine physical drives in three arrays, with one global hot spare. 12

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Chapter 2
RAID Overview
12
Arrays can combine disk drives that are all on one channel of an
HP NetRAID-1M or 2M adapter, or they can combine disk drives from both
channels of an HP NetRAID-2M adapter. However, all the disk drives in an array
must be connected to a single NetRAID adapter. Using internal connectors, this
means that the maximum number of disk drives in an array is 6 (HP NetRAID-
1M) or 12 (HP NetRAID-2M). Using external connectors, the maximum number
of disk drives in an array is 12 (HP NetRAID-1M) or 24 (HP NetRAID-2M).
Hot Spares
A hot spare is a powered-on, stand-by disk drive that is ready for use should
another disk drive fail. When a disk fails, the HP NetRAID adapter’s firmware
can automatically rebuild the data from the failed disk onto the hot spare. The
system administrator can then replace the failed disk and designate a new hot
spare disk. Until a rebuild occurs, a hot spare does
not
contain user data.
There are two types of hot spares:
•
A global hot spare is used if a disk in any array on the adapter fails.
•
A dedicated hot spare is reserved for use by a single array.
Logical Drives
The term "logical drive" refers to a virtual drive that is assigned some portion of
the total capacity of an array. For example, if you have an array of disk drives
with a total capacity of 80 GB, you can create a logical drive with a total capacity
of 20-GB within that array.
Logical drives can take three forms:
•
A logical drive can use all of the storage capacity of one array. In
Figure 2-3, Logical Drive LD0 uses all storage capacity in Array A0.
•
A logical drive can use less than the available storage capacity of one
array. In Figure 2-3, Logical Drive LD1 occupies only a part of Array A1.
•
A logical drive can span arrays by spreading across up to eight different
arrays. In Figure 2-3, Logical Drive LD2 spans Arrays A1 and A2.
In Figure 2-3, there are nine physical drives in three arrays, with one global hot
spare.