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# Cache Partition metrics

Unisphere collects and displays metrics for cache partitions.

Cache partition metrics are supported only by storage systems (arrays) running HYPERMAX OS 5977 or PowerMaxOS 5978.

The following table lists all metrics that are available for cache partitions.

Table 1. Cache partition metrics
Metric | Description
--- | ---
% Cache Used | The percentage of the cache partition that is used
% Hit | The percentage of I/O operations that were immediately satisfied from cache
% Max Cache | Maximum slot allocation for a partition
% Min Cache | Minimum slot allocation for a partition
% Target Cache | Percentage of total cache that is allocated to this partition
% WP Utilization | The percent of tracks in cache that are write-pending. Until the data is destaged to disk, those tracks are not used to serve reads and improve the hit ratio
Acquired Slot Count | Slots acquired from another partition
Age Non WP Slots | Average age of non-write pending slots
Avg Age Given Destage | Average age given de-stage
Avg Age of Write to Non WP Slot | (age non wp slots) / ((writes to all non wp slots) - (writes to young non wp slots))
Cache Age GT 1 hour | Average FTT with 1:08:16 decay—Decay is a moving average where the decay time is the average time average.
Cache Age GT 1 Min | Average FTT with 64 sec decay—Decay is a moving average where the decay time is the average time average.
Cache Age GT 10 Min | Average FTT with 8:32 decay—Decay is a moving average where the decay time is the average time average.
Cache Hit Ages 1 | Partition RH under 4 sec. A slot in this age range satisfied a host read request (cache hit) and was promoted to age zero
Cache Hit Ages 2 | partition 4 < RH <= 8 s
Cache Hit Ages 3 | partition 8 < RH <= 16 s
Cache Hit Ages 4 | partition 16 < RH <= 32 s
Cache Hit Ages 5 | partition 32 < RH <= 1:04
Cache Hit Ages 6 | partition 1.04 < RH <= 2:08
Cache Hit Ages 7 | partition 2:08 < RH <= 4:16
Cache Hit Ages 8 | partition 4:16 > RH
Cache Slot Ages 1 | partition FT under 8 sec. a slot in this age range was removed or recycled as a new slot for other data
Cache Slot Ages 2 | partition 8 < FT < 16 s
Cache Slot Ages 3 | partition 16 < FT <= 32 s
Cache Slot Ages 4 | partition 32 < FT <= 1:04
Cache Slot Ages 5 | partition 1:04 < FT <= 2:08
Cache Slot Ages 6 | partition 2:08 < FT <= 4:16
Cache Slot Ages 7 | partition 4:16 < FT <= 8:32
Cache Slot Ages 8 | partition 8:32 > FT
Cache Slots Used | Cache slots used
Destage Slot Age | Destage slot age
Destaged Slot Count | Destaged slot count
Donation Give Count | Destaged give count
Donation Take Count | Donation take count
Donation Time | Length of time before idle cache is made available to other partitions
Host IOs/sec | Host operations performed each second by the cache partition
Host MBs/sec | The number of host MBs written and read each second
Local WP Count | The number of write pending slots waiting to be de-staged to disk on the local system. The value should be less than or equal to the system write pending count
Local WP Used Capacity | Local WP Used Capacity
Remote WP count | The number of write pending slots waiting to be de-staged to disk on the remote system. The value should be less than or equal to the system write pending count
Remote WP Used Capacity | Remote WP Used Capacity
Total Replace Slots | Total replaces slots
WP Count | The number of cache partition slots that are write-pending
WP Limit | The maximum number of write-pending slots
WP Used Capacity | WP Used Capacity
Writes to All Non WP Slots | Writes to all non-WP slots
Writes to Young Non WP Slots | Writes to young non-WP slots