User guide

Compaq StorageWorks RAID Array 4000 User Guide
Drive arrays have several important attributes:
■ A single array cannot span more than one RA4000 Controller.
■ A single RA4000 Controller can control multiple arrays.
■ Arrays must have at least one and may have up to 12 physical drives.
■ Arrays will consist of at least one and may have up to 32 logical drives
(maximum 32 logical drives per controller).
■ For maximum space efficiency, all drives in a single array should be the
same capacity.
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 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 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 portion 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.
The benefits of using drive arrays include: