HP StorageWorks Command View SDM Installation and User Guide (T1086-96023, February 2005)

172 Command Line User Interface
RAID 5 DP Allocation (1.05
release)
RAID 5 DP Capacity (absolute)
(prior to 1.05)
ARRAY The number of logical blocks in the array that are stored
using the RAID 5 DP storage method. It is a sum of the
RAID 5 DP Allocation metrics from each configured LUN.
Usage
RAID 5 DP provides better storage efficiency than RAID
1+0 and approximately equivalent sequential write
performance. AutoRAID will attempt to detect a sequential
write workload and store the data in RAID 5 DP to get
better storage efficiency. As the array becomes filled with
data AutoRAID will migrate more of the data to RAID 5
DP. AutoRAID preserves a minimum of 10% of the data in
RAID 1+0 when the array is completely full. The more data
stored in RAID 1+0 as compared to RAID 5 DP, the better
the random write performance that can be achieved.
AutoRAID policies will migrate the write working set into
RAID 1+0 for better random write performance. If better
random write performance is needed in an AutoRAID
configuration, adding more disks to the array may
provide enough space to fit the write working set into
RAID 1+0 providing better random write performance.
This metric can be compared with the RAID 1+0 DP
Capacity metric to determine the overall distribution of
data across the two storage methods. Space that has been
allocated to configured LUN's but has not been written to
yet will not be counted in either the RAID 5 DP Allocation
or the RAID 1+0 DP Capacity metrics. The sum of these
two metrics can be compared to the total capacity
allocated to configured LUN's to determine how “full” the
array is.
RAID 5 DP to RAID 1+0
Relocations Spawned by
MakeSpace
OPAQUE The number of clusters that were relocated by the make
space policy from RAID 5 DP to RAID 1+0 storage.
Usage
RAID 1+0 has less storage efficiency than RAID 5 DP so
relocating data from RAID 1+0 to RAID 5 DP does not
contribute to the goal of the make space policy. One of
these relocations may occur in the case that a RAID 5 DP
to RAID 5 DP relocation was interrupted by an error.
Table 12 Performance Metrics (Continued)
Metric Categories Description/Usage