HP Surestore Disk Array 12h - And FC60, Advanced User'S Manual, Page: 58 / 466

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Disk Array High Availability Features
* Compares the relative read and write performance for array configurations with the
performance of a single stand-alone disk whose performance is 1.0. The read and write
performance shown is the theoretical maximum performance relative to individual disk
performance. The performance numbers are not based on read/write caching. With caching,
the performance numbers for RAID 5 writes improve significantly.
Table 2
RAID Level Comparison: Storage Efficiency Characteristics
RAID Level Storage Efficiency
RAID 0 100%. All disk space is use for data storage.
RAID 1 and 0/1 50%. All data is duplicated, requiring twice the disk storage for a
given amount of data capacity.
RAID 3 and 5 One disk’s worth of capacity from each LUN is required to store
parity data. As the number of disks in the LUN increases, so does
the storage efficiency.
3-disk LUN: 66%
4-disk LUN: 75%
5-disk LUN: 80%
6-disk LUN: 83%
Table 3
RAID Level Comparison: Relative Performance Compared to an Individual Disk*
LUN Configuration
Relative Read Performance
for Large Sequential Access Relative Write Performance
for Large Sequential Access
RAID 0 The read and write performance of a RAID 0 LUN increases as
the multiple of the number of disks in the LUN. For example, a
4-disk RAID 0 LUN will achieve close to four times the
performance of a single disk.
RAID 1 mirrored pair Up to 2.0 > than single disk Equal to single disk
RAID 0/1 group with 10 disks Up to 10.0 > than single disk Up to 5.0 > than single disk
RAID 0/1 group with 6 disks Up to 6.0 > than single disk Up to 3.0 > than single disk
RAID 3 group with 5 disks Up to 4.0 > than single disk Up to 1.25 > than single disk
RAID-5 group with 5 disks Up to 4.0 > than single disk Up to 1.25 > than single disk