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Dell Storage Technology Foundations Online Training Course
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Array Manager
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Working with RAID

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Storage Management

Working with RAID

In addition to the standard RAID levels (RAID 0, 1, 5, 10, and 50), Array Manager supports concatenation. Concatenation refers to storing data on either one disk or on disk space that spans multiple array disks. When spanning more than one disk, concatenation enables the operating system to view multiple array disks as a single disk.

When an array disk in a concatenated or spanned volume fails, the entire volume becomes unavailable. Because the data is not redundant, it cannot be restored by rebuilding from a mirrored disk or parity information. Restoring from a backup is the only option.

NOTE Note: RAID 10 on the PERC 3/DCL, 3/DC, and 3/QC is implemented as a RAID-1 Concatenated. Instead of first striping data to each mirror set, it is concatenated across each mirror set. No striping is involved.

Disk Coercion
It is best to create virtual disks on drives of the same size. Different sized drives can be used but the PERC will coerce or will use a size common to all disks. For example, if want to configure a RAID-5 across two 18GB drives and one 9GB drive, the PERC will only use 9GB from each drive. 9GB is the size that all three drives support so it is what the PERC will use.
Battery Reconditioning
The PERC 3/Di has a battery to protect the cache memory in the event of a power failure. This battery must be reconditioned periodically to ensure optimal performance. Array Manager is used to recondition the battery. During battery reconditioning, the cache memory is disabled. Because of this, it is recommended to recondition the battery during off peak hours. The PERC will prompt you when the battery needs reconditioning.
Consistency Checks
A consistency check when initiated checks mirror synchronization and rebuilds parity if necessary. A consistency check is considered preventative maintenance and it is recommended that you do not access any volumes on a virtual disk during the check.
Hot Spares
A hot spare is an unused backup array disk. It remains in a standby mode until a virtual disk fails. The hot spare is then activated and replaces the failed array disk without interrupting the system or requiring intervention. There are two types of hot spares:

  • Global - A hot spare that is a backup for any physical disk in the array.

  • Dedicated - A hot spare that is a backup for an array disk in a specific virtual disk.

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