Logical Drives - Compaq Smart Array 221 User Manual

C-4 Understanding Drive Arrays

Logical Drives

The concept of logical drives is an important one. A logical drive is storage
space that is distributed across all physical drives in an array (except for online
spares). See Figures C-1 through C-4. Distributing the storage space provides
these advantages:
Data can be accessed on all the physical drives at once, resulting in much
higher performance data storage and retrieval.
Fault tolerance methods may be used to protect your data against
hardware failures.
An array can consist of several logical drives, each spanning all of the physical
drives in the array. It is important to note that the part of any one logical drive
residing on each physical drive is the same size. This means that for maximum
space efficiency, all physical drives in each array should also be the same size.
Logical drives have these important attributes:
There must be at least one and up to 32 logical drives in an array
(maximum 32 logical drives per controller).
Logical drives in an array may be different sizes.
Logical drives in an array may use different fault tolerance methods
(RAID levels).
The portion of a logical drive on each physical drive is the same size.
Writer: Karen Hale Project: Compaq Smart Array 221 Controller User Guide Comments: 388541-001
File Name: K-APPC.DOC Last Saved On: 11/5/98 1:40 PM
COMPAQ CONFIDENTIAL - NEED TO KNOW REQUIRED