D-4
Understanding Drive Arrays
Writer: Pamela King Project: SMART-2DH Array Controller Reference Guide Comments: 295469-002
File Name: K-APPD.DOC Last Saved On: 2/27/98 12:06 PM
COMPAQ CONFIDENTIAL - NEED TO KNOW REQUIRED
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 Figure D-3.) 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.
