Cache Hit Rates - HPE XP7 User Manual

Cache hit rates

Function
The cache hit rate is a rate that the input or output data of the disk exists in the cache. The cache
hit rate is displayed for the sequential access mode, the random access mode, the cache fast
write (CFW) mode, and the entire these modes.
Read hit ratio
For a read I/O, when the requested data is already in cache, the operation is classified as
a read hit. For example, if ten read requests have been made from hosts to devices in a
given time period and the read data was already on the cache memory three times out of
ten, the read hit ratio for that time period is 30 percent. A higher read hit ratio implies higher
processing speed because fewer data transfers are made between devices and the cache
memory.
Write hit ratio
For a write I/O, when the requested data is already in cache, the operation is classified as
a write hit. For example, if ten write requests were made from hosts to devices in a given
time period and the write data was already on the cache memory three cases out of ten, the
write hit ratio for that time period is 30 percent. A higher write hit ratio implies higher
processing speed because fewer data transfers are made between devices and the cache
memory.
Storing period
Short-Range can be specified.
Selection of monitoring objects
Select the desired monitoring objects in the Performance Objects field.
Item on left side of Object
field
Logical Device*
Parity Group*
42 Performance Monitor data
Item on right side of
Object field
Base
Cnt Ac-J/Cnt Ac-J MF
None
Item on left side of
Monitor Data field
Cache Hit (%)
Initial Copy
Cache Hit (%)
Item on right side of
Monitor Data field
Read (Total)
Read (Sequential)
Read (Random)
Read (CFW)
Write (Total)
Write (Sequential)
Write (Random)
Write (CFW)
Cache Hit (%)
Read (Total)
Read (Sequential)
Read (Random)
Read (CFW)
Write (Total)
Write (Sequential)