Mylex DAC960PG, Installation Manual

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Functional Description
Manual No. 771971 2-17
Striping with Mirroring (RAID 0+1)
RAID 0+1 (Mylex RAID 6) is a combination of RAID 0 (striping) and
RAID 1 (mirroring).
The advantages of RAID 0+1 are fully mirrored data and better performance
than RAID 1. The disadvantage of RAID 0+1 is its 50% utilization capacity
(if all drives are the same size).
Striping Terminology
Stripe Width
The number of drives within a drive group is referred to as the stripe width.
Stripe Order
The order in which SCSI drives appear within a drive group is the stripe
order. It is critical that the selected stripe order is always maintained, to
assure data integrity and the controller's ability to rebuild failed drives.
Stripe Size
The size of the logically contiguous data block recorded on each drive within
a logical unit is the stripe size. The default is 8 KBytes. Other choices are 16,
32, or 64 KBytes, which may be selected from the DACCF configuration
utility (Advanced Functions menu, Physical Parameters option), or from the
GAM.
Larger stripe size ensures better performance for large sequential data
transfers. Smaller stripe size is best suited for small random data transfers.
Disk 0 Disk 1 Disk 2
Stripe 0
Sectors 0-F
Stripe 1
Sectors 10-1F
Stripe 2
Sectors 20-2F
Stripe 2
Sectors 20-2F
Stripe 0
Sectors 0-F
Stripe 1
Sectors 10-1F
Stripe 3
Sectors 30-3F
Stripe 4
Sectos 40-4F
Stripe 5
Sectors 50-5F
Stripe 5
Sectors 50-5F
Stripe 3
Sectors 30-3F
Stripe 4
Sectos 40-4F