Promise Technology Network Device EX8654 - Manual (Page 238)

SuperTrak EX Series User Manual
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RAID 6 – Block and Double Parity Stripe
RAID level 6 stores dual parity data is rotated across the physical drives along
with the block data. A RAID 6 logical drive can continue to accept I/O requests
when any two physical drives fail.
Figure 5. RAID 6 stripes all drives with data and dual parity
The total capacity of a RAID 6 logical drive is the smallest physical drive times
the number of physical drives, minus two.
Hence, a RAID 6 logical drive with (7) 100 GB physical drives will have a capacity
of 500 GB. A RAID 6 logical drive with (4) 100 GB physical drives will have a
capacity of 200 GB.
RAID 6 becomes more capacity efficient in terms of physical drives as the
number of physical drives increases.
RAID 6 provides double fault tolerance. Your logical drive remains available
when up to two physical drives fail.
RAID 6 is generally considered to be the safest RAID level.
A RAID 6 on SuperTrak consists of 4 to 16 physical drives.
Double Distributed (P and Q) Parity
physical drives
Data
Blocks