HP Command View EVA Software - Manual (Page 94)

management, or communication with other applications. The value is always equal to or less
than the % Processor Time counter and the difference is the amount of processor time engaged
in non-data transfer activity.
HP EVA virtual disk
The virtual disk object provides information about workload and performance for each virtual disk
on the storage system. Activity is reported separately for each controller accessing a virtual disk.
The total activity for each virtual disk is the sum of the reported activity for each controller. A virtual
disk may also be a snapshot, snapclone, or a DR group member. In the output, logical unit number
(LUN) is used interchangeably with virtual disk.
Virtual disks must be presented to a host to be seen by HP P6000 Performance Data Collector.
However, replication volumes on the replication system are visible without being presented. HP
P6000 Performance Data Collector also shows DR group membership with the virtual disk table
in the DRM Group column.
If the storage system controllers are active/standby, all activity to a virtual disk is through the active
controller. If the storage system controllers are active/active, one controller is preferred (the owning
controller) but requests can still be processed by the other controller (the proxy controller). In
active/active controllers, all host requests are logged by the receiving controller only, whether
owning or proxy. Thus, all request rate and data rate activity for a virtual disk is the sum of both
controllers.
The counters are:
•
Read Hit Req/s —The number of read requests per second completed from the storage
system cache memory. Data may reside in the cache memory due to a previous cache miss
or because of a prefetch operation generated by a sequential read data stream.
•
Read Hit MB/s —The rate at which data is read from the storage system cache memory
because of read hit requests.
•
Read Hit Latency —The average time it takes to complete a read request (from initiation
to information receipt) from the storage system cache memory.
•
Read Miss Req/s —The number of read requests (per second) that failed to complete from
the storage system 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 storage system cache memory.
•
Read Miss Latency —The average time it takes to complete a read request (from initiation
to information receipt) from the physical disks.
•
Write Req/s —The number of write requests per second completed to a virtual disk that
were received from all hosts. Write requests may include transfers from a source storage
system to this storage system for data replication 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 storage system to the destination storage system.
•
Write Latency —This average time it takes to complete a write request (from initiation to
receipt of write completion).
•
Flush MB/s —The rate at which data is written to physical storage. Data replication data
written to the destination volume is included in the flush statistics. Host writes to snapshot and
snapclone volumes are included in the flush statistics. However, data flow for internal snapshot
and snapclone normalization and copy-before-write activity is not included.
•
Mirror MB/s —The rate at which data moves across the mirror port in servicing read and
write requests to a virtual disk. Write data is always copied through the mirror port when
cache mirroring is enabled for redundancy. The mirror data rate includes read data from the
94 Monitoring array performance using HP P6000 Performance Data Collector