Planning: MD3200 Series Storage Array Terms and Concepts 41
Segment Size
Disk striping enables data to be written across multiple physical disks. Disk
striping enhances performance because striped disks are accessed
simultaneously.
The segment size or stripe element size specifies the size of data in a stripe
written to a single disk. The MD3200 Series array supports stripe element
sizes of 8, 16, 32, 64, 128, 256, and 512 KB. The default stripe element size is
128 KB.
Stripe width, or depth, refers to the number of disks involved in an array
where striping is implemented. For example, a four-disk group with disk
striping has a stripe width of four.
NOTE: Although disk striping delivers excellent performance, striping alone does
not provide data redundancy.
Virtual Disk Operations
Virtual Disk Initialization
Every virtual disk must be initialized. Initialization can be done in the
foreground or the background. A maximum of four virtual disks can be
initialized concurrently on each RAID controller module.
Background Initialization
The storage array executes a background initialization when the virtual disk is
created to establish parity, while allowing full host server access to the virtual
disks. Background initialization does not run on RAID 0 virtual disks. The
background initialization rate is controlled by MDSM. To change the rate of
background initialization, you must stop any existing background
initialization. The rate change is implemented when the background
initialization restarts automatically.
Foreground Initialization
The storage array supports foreground initialization for virtual disks. All
access to the virtual disk is blocked during foreground initialization. During
foreground initialization, zeros (0x00) are written to every sector of the virtual
disk. The virtual disk is available after foreground initialization is completed.
book.book Page 41 Monday, June 21, 2010 11:00 AM
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