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E-4 Understanding Drive Arrays
Writer: Rickard Project: Compaq Smart Array 3200 Controller Reference Guide Comments: 340862-002
File Name: L-APPE.DOC Last Saved On: 12/7/98 9:30 AM
COMPAQ CONFIDENTIAL - NEED TO KNOW REQUIRED
Logical Drives
A logical drive is storage space that is distributed across all physical drives in an
array (except for online spares). Refer to Figure E-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 can be used to protect your data against
hardware failures.
An array can consist of several logical drives, each spanning all 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 always be the same size.
The following are important characteristics of logical drives:
■ There must be at least one logical drive and up to 32 logical drives in an
array (maximum 32 logical drives per controller).
■ Logical drives in an array can be different sizes.
■ Logical drives in an array can use different fault-tolerance methods
(RAID levels).
■ The portion of a logical drive on each physical drive is the same size.