Specifications

Chapter 2 RAID Overview
17
Spanned Arrays: RAID Levels 10 and 50
With HP NetRAID-1M and 2M adapters, array spanning allows the capacity of
up to eight basic arrays to be combined into a single storage space. A spanned
array configuration must have the same number of disk drives in each basic
array. For example, a RAID 5 array containing three drives cannot be combined
with a RAID 5 array containing six drives.
RAID 10: Spanning with Mirrored Arrays
A RAID 10 configuration combines multiple RAID 1 arrays into a single storage
space. The data is mirrored within each RAID 1 array and striped across all the
RAID 1 arrays that constitute the RAID 10 logical drive. For example, if your
RAID 10 configuration spans two RAID 1 arrays, data blocks are written as
follows:
Spanned Array (RAID 10)
Array 1 (RAID 1) Array 2 (RAID 1)
Disk 1 Disk 2 Disk 3 Disk 4
Stripe 1
Block 1Block 1Block 2Block 2
Stripe 2
Block 3Block 3Block 4Block 4
Stripe 3
Block 5Block 5Block 6Block 6
RAID 10 Advantages
• There is no data loss or system interruption due to disk failure, because if
one disk fails, its mirror image is available.
• Read performance is fast, because data is available from either disk in each
pair.
• RAID 10 lets you create large logical drives:
♦ With the HP NetRAID-1M adapter, the total number of disks in the
RAID 10 logical drive is limited by the number of disks that can be
attached to a single SCSI channel. For example, if the Rack Storage/12
enclosure is used, the maximum number of disks in a RAID 10 logical
drive is 12.
♦ With the HP NetRAID-2M adapter, you can span up to eight RAID 1
arrays, resulting in a 16-disk RAID 10 logical drive.