HP StorageWorks 4x00/6x00/8x00 Enterprise Virtual Array Updating Product Software Guide XCS 6.110 (5697-6782, June 2007)

Figure 7 Sample virtual disk sta tistics display
Table 6 HP Command View EVAPerf virtual disk statistics
Counter Description
Read Hit Req/s The number of read requests per second com
pleted from the array cache
memory. Data may reside in the cache memor
yduetoapreviouscachemissor
because of a prefetch operation generate
d by a sequential read data stream.
Read Hit MB/s The rate at which data is read from the array cache memory because of read
hit requests.
Read Hit Latency
Theaveragetimeittakestocompleteareadrequest(frominitiationto
information receipt) from the array cache memory.
Read Miss Req/s The number of read requests (per second) that failed to complete from the array
cache memory and were completed from physical disks instead.
Read Miss Data Rate
The rate at which data is read from physical disks because the data was not
present in the array cache memory.
Read Miss Latency
Theaveragetimeittakestocompleteareadrequest(frominitiationto
information receipt) from t he physical disks.
Write Req/s The number of write requests per secon
d completed to a virtual disk that we re
received from all hosts. Write reque
sts may include transfers from a source
array to this array for data replicat
ion and host data written to snapshot or
snapclone volumes.
Write Data Rate
The rate at which data is written to the virtual disk by all hosts and includes
transfers from the source array to the destination array.
Write Latency
This average time it takes to complete a write request (from initiation to receipt
of write completion).
Flush Data Rate
Therateatwhichdataiswrittento
aphysicaldiskfortheassociatedvirtual
disk. The sum of flush counters for a
ll virtual disks on both controllers is the rate
at which data is written to the phys
ical drives and is equal to the total host
write data. Data written to the de
stination array is included. Host writes to
snapshots and snapclones are in
cluded in the flush statistics, but data flow for
internal snapshot and snapclon
e normalization and copy-before-write activity
are not included.
Mirr or Data Rate
The rate at which data travels across the mirror port to complete read and write
requests to a virtual disk. This data is not related to the physical disk mirroring
for Vraid1 redundancy. Write data is always copied through the mirror port
when cache mirroring is enabled for redundancy. In active/active controllers,
this counter includes read data from the owning controller that must be returned
to the requesting host through the proxy controller. Reported mirror traf ficis
always outbound from the referenced controller to the other controller.
Prefetch Data Rate The rate at which data is read from the physical disk to cache in anticipation of
subsequent reads when a sequential stream is detected. Note that a sequential
data stream may be created by host I/O and other I/O activity that occurs
becauseofaDRinitialcopyorDRfullcopy.
HP StorageWorks 4x00/6x00/8x00 Enterprise Virtual Array updating product software guide XCS 6.110
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