Promise Technology SmartStor NAS Product Manual page 215

RAID 5 - Block Striping with Distributed Parity
RAID 5 organizes block data and parity data across the disk drives. Generally,
RAID level 5 tends to exhibit lower random write performance due to the heavy
workload of parity recalculation for each I/O. RAID 5 works well for file, database,
application and web servers.
Data
Blocks
Figure 3. RAID 5 Stripes all drives with data and parity information
The capacity of a RAID 5 Volume equals the smallest disk drive times the
number of disk drives, minus one. Hence, a RAID 5 Volume with four 100 GB
disk drives will have a capacity of 300 GB. A RAID Volume with two 120 GB disk
drives and one 100 GB disk drive will have a capacity of 200 GB.
RAID 5 is generally considered to be the most versatile RAID level.
RAID 5 requires a minimum of three disk drives.
RAID 10 - Mirror / Stripe
Mirror/Stripe combines both of the RAID 0 and RAID 1 types. RAID 10 can
increase performance by reading and writing data in parallel while protecting
data with duplication. At least four disk drives are needed for RAID 10 to be
installed.
With a four-disk-drive RAID Volume, one drive pair is mirrored together then
striped over a second drive pair.
Chapter 7: Technology Background
Distributed Parity
disk drives
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