Mixing Raid Configurations; Data Availability And Safety In Raid Configurations - HP StorageWorks P4000 User Manual

NOTE:
If you are protecting volumes across a cluster, configuring the storage system for RAID 1 or RAID 10
consumes half the capacity of the storage system. Configuring the storage system for RAID 5 or RAID
50 provides redundancy within each storage system while allowing most of the disk capacity to be
used for data storage. RAID 6 provides greater redundancy on a single storage system, but consumes
more disk space than RAID 5.
Table 12 on page 58 summarizes the differences in data availability and safety of the different RAID
levels on stand-alone storage systems compared with those RAID levels with Network RAID configured
volumes in a cluster.
Table 12 Data availability and safety in RAID configurations
Configuration
Stand-alone storage systems, RAID 0
Stand-alone storage systems, RAID 1,
RAID 10, RAID 10 + spare
Stand-alone storage systems, RAID 5,
RAID 5 + spare, RAID 50
Stand-alone storage systems, RAID 6
Volumes configured with Network RAID-
10 or greater on clustered storage sys-
tems, RAID 0
Volumes configured with Network RAID-
10 or greater on clustered storage sys-
tems, RAID 5, RAID 50
Volumes configured with Network RAID-
10 or greater on clustered storage sys-
tems, RAID 6
Volumes configured with Network RAID-
10 or greater on clustered VSAs with
virtual RAID

Mixing RAID configurations

You may mix storage systems with different configurations of RAID within a cluster. This allows you
to add new storage systems with different RAID levels. However, be certain to calculate the capacity
of additional storage systems configured with the desired RAID level, because the cluster operates at
the smallest usable per-storage system capacity.
58 Storage Configuration: Disk RAID and Disk Management
Data safety and availability during
disk failure
No
Yes. In any configuration, 1 disk per
mirrored pair can fail.
Yes, for 1 disk per array
Yes, for 2 disks per array
Yes. However, if any disk in the storage
system fails, the entire storage system must
be copied from another storage system in
the cluster.
Yes. 1 disk per RAID set can fail without
copying from another storage system in
the cluster.
Yes. 2 disks per RAID set can fail without
copying from another storage system in
the cluster.
Depends on the underlying RAID configur-
ation of the storage system on which the
VSA is installed. HP recommends configur-
ing RAID 5 or RAID 6.
Data availability if
entire storage system
fails or if network
connection to stor-
age system lost
No
No
No
No
Yes
Yes
Yes
Yes, if underlying stor-
age system configured
for RAID other than
RAID 0.