HP 3PAR StoreServ Concepts Guide: HP 3PAR OS 3.1.3

failures. When the destination LDs become available again, the system automatically writes the
preserved data from the preserved data LDs to the destination LDs.
• Administration volume LDs provide storage space for the admin volume, a single volume
created on each system during installation. The admin volume is used to store system
administrative data such as the system event log.
RAID Types
The 3PAR storage system supports the following RAID types:
• RAID 0
• RAID 10 (RAID 1)
• RAID 50 (RAID 5)
• RAID multi-parity (MP)
RAID 0
On a RAID 0 LD, data is striped across rows of chunklets on different physical disks. The number
of chunklets in a RAID 0 set is the set size, which is always 1 for a RAID 0 LD. The number of sets
in a row is the row size. The system accesses data from a RAID 0 LD in step sizes, where the step
size is the number of contiguous bytes that the system accesses before moving on to the next
chunklet. A RAID 0 LD improves performance but provides no fault-tolerance.
Figure 5 (page 37) shows a RAID 0 LD with a set size of 1 and a row size of 3.
Figure 5 Data Striped Across Chunklets on a RAID 0 LD
RAID 1 and RAID 10
On a RAID 10 LD, data is striped across RAID 1 (or mirrored) sets. A RAID 1 set is made up of
two or more chunklets that contain the same data. The chunklets in each set are distributed across
different physical disks, which may be located in different drive magazines or even different drive
cages. The number of chunklets in a RAID 1 set is the set size, or mirror depth. The number of sets
in each row is the row size. The maximum row size is 40. The system accesses data from a RAID
10 LD in step sizes. A step size is the number of contiguous bytes that the system accesses before
moving on to the next chunklet. A RAID 1 set can function with the loss of all but one of the chunklets
in the set.
Figure 6 (page 38) shows a RAID 10 LD with a set size of 2 and a row size of 3 in two rows:
RAID Types 37