HP StorageWorks All-in-One SB600c Storage Blade - Manual (Page 29)

• For user-defined applications and shared folders (where industry-standard recommendations
cannot be determined), the wizard provides default settings you can customize.
Table 7 shows how the different RAID levels affect:
• Performance–The speed at which data is read from and written to the hard drives. The RAID level
with the best performance rating provides the fastest reads and writes.
• Capacity–The available storage space on the hard drives. The RAID levels with the best capacity
rating require the least amount of storage space to store data.
• Data protection–The number of hard drives that can fail without data being lost. The RAID level
with the best data protection rating allows more hard drives to fail before data is lost.
For more information on the different RAID levels, see Table 7 .
Table 7 Descriptions of RAID levels
RAID level Description
No RAID
Offers no protection against disk failure. If a disk drive fails, data
will be lost.
RAID 0 – Striping (No Fault Tolerance)
Offers the greatest capacity and performance without data protection.
If you select this option, you will experience data loss if a hard drive
that holds the data fails. However, because no logical drive capacity
is used for redundant data, this method offers the best capacity. This
method offers the best processing speed by reading two stripes on
different hard drives at the same time and by not having a parity
drive.
RAID 1 – Mirroring
Offers a good combination of data protection and performance.
RAID 1 or drive mirroring creates fault tolerance by storing duplicate
sets of data on a minimum of two hard drives. There must be an even
number of drives for RAID 1. RAID 1 and RAID 1+0(10) are the most
costly fault tolerance methods because they require 50 percent of
the drive capacity to store the redundant data. RAID 1 mirrors the
contents of one hard drive in the array onto another. If either hard
drive fails, the other hard drive provides a backup copy of the files
and normal system operations are not interrupted.
RAID 1+0 – Mirroring and Striping
Offers the best combination of data protection and performance.
RAID 1+0 or drive mirroring creates fault tolerance by storing
duplicate sets of data on a minimum of four hard drives. There must
be an even number of drives for RAID 1+0. RAID 1+0(10) and RAID
1 are the most costly fault tolerance methods because they require
50 percent of the drive capacity to store the redundant data. RAID
1+0(10) first mirrors each drive in the array to another, and then
stripes the data across the mirrored pair. If a physical drive fails,
the mirror drive provides a backup copy of the files and normal
system operations are not interrupted. RAID 1+0(10) can withstand
multiple simultaneous drive failures, as long as the failed drives are
not mirrored to each other.
RAID 5 – Distributed Data Guarding
Offers the best combination of data protection and usable capacity
while also improving performance over RAID 6. RAID 5 stores parity
data across all the physical drives in the array and allows more
simultaneous read operations and higher performance than data
guarding. If a drive fails, the controller uses the parity data and the
data on the remaining drives to reconstruct data from the failed drive.
The system continues operating with a slightly reduced performance
until you replace the failed drive. RAID 5 can only withstand the loss
of one drive without total array failure. It requires an array with a
minimum of three physical drives. Usable capacity is N-1 where N is
the number of physical drives in the logical array.
RAID 6– Advanced Data Guarding
(ADG)
Offers the best data protection and is an extension of RAID 5. RAID
6 uses multiple parity sets to store data and can therefore tolerate up
to 2 drive failures simultaneously. RAID 6 requires a minimum of 4
drives and is available only if the controller has an enabler. Writer
All-in-One Storage Manager 29