Explaining raid devices in the raid setup report – HP LeftHand P4000 SAN Solutions User Manual
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Table 6 Descriptions of RAID levels (continued)
Description
RAID level
data. RAID 1+0 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 can withstand multiple simultaneous
drive failures, as long as the failed drives are not mirrored to each other.
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
RAID 5
and allows more simultaneous read operations and higher performance. 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 storage 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.
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
RAID 6
a minimum of 4 drives. Performance is lower than RAID 5 due to parity data updating on
multiple drives. RAID 6 uses two disk for parity; its fault tolerance allows two disks to fail
simultaneously. Usable capacity is N-2 where N is the number of physical drives in the logical
array.
Used with the StoreVirtual VSA, Stripe stores data across all of the drives in a RAID-0-like
fashion. The underlying storage of the StoreVirtual VSA should be configured with redundant
RAID to prevent single disk failures.
Stripe
NOTE:
The HP StoreVirtual 4335 has two RAID levels available, RAID 5 and RAID 6. By default,
it comes configured with RAID 5. If you reconfigure the HP StoreVirtual 4335 storage system with
RAID 6, the SAS drives, numbers 1 through 7, will be configured with RAID 6. The three SSD
drives, numbers 8 through 10, will remain at RAID 5, since RAID 6 requires a minimum of four
drives.
Explaining RAID devices in the RAID setup report
In the Storage category, the RAID Setup tab lists the RAID devices in the storage system and provides
information about them. An example of the RAID setup report is shown in
Information listed in the report is described in
Figure 8 RAID setup report
RAID devices by RAID type
Each RAID type creates different sets of RAID devices.
contains a description
of the variety of RAID devices created by the different RAID types as implemented on various
storage systems.
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Configuring RAID and Managing Disks