Cache capacity tube

The cache capacity tube on the main view displays cache allocation and management information.

The capacity tube displays a representation of used (blue areas) and unused (grey area) cache, including cache group allocations. Hover over a section of the cache capacity tube to display a tooltip that contains information about any cache item represented on the capacity tube. If the cache contains multiple used cache items, the tooltip displays them all but uses bold text to identify the item receiving hover focus. Cache items displayed on the capacity tube can differ based on the model of the active cluster, as shown in Table 1.
Table 1. Cache capacity tube items
Cluster model Cache item Description
Any Licensed Capacity The maximum licensed amount of cache available. The capacity tube displays this amount as its upper limit, represented by the grey area of the tube.
TS7700 Cluster not attached to a physical library
Note: When the TS7700 is not attached to a physical library, used cache shown is described by retention groups. These groups are set by Storage Class constructs. Retention groups determine when a volume will be removed from cache and returned to scratch, based on cache capacity and the existence of another copy in cache.

If the TS7700 Cluster is attached to a physical library, the only cache values shown are Licensed Capacity and Total Physical Used.

Prefer Remove The total amount of cache that contains volumes marked Prefer Remove, which are removed first when the cache reaches a predetermined capacity and no scratch-ready volumes exist.
Prefer Keep The total amount of cache that contains volumes marked Prefer Keep, which are the last to be removed when the cache reaches a predetermined capacity and no scratch-ready volumes exist.
Pinned The total amount of cache that contains volumes marked Pinned, which are never removed from cache.
Flash Copy The total amount of cache that contains Flash Copy volumes, which can be present if Write Protect Mode is enabled by a host LI REQ command and disaster recovery testing has begun.
Lower Removal Threshold A pink line representing a removal threshold that has been temporarily lowered for all TS7700 Clusters in the grid not attached to a physical library.
TS7700 Cluster Total Physical Used The actual amount of all used cache, shown as a number and a percentage of Licensed Capacity. This value includes the size of metadata storage.
TS7700 Tape Attach Cluster
Note: If the selected cluster is a TS7700 Tape Attach, used cache shown can be one of two tape volume preference groups (PG0 or PG1) depending on the Storage Class construct to which a virtual volume is assigned. These groups define how cache is migrated to tape.
Prefer Migrate (PG0) The total amount of cache defined using PG0. If no other preference groups are used, this value is equal to the Total Physical Used amount minus the size of metadata storage. Volumes in this group have preference to be removed from cache over other volumes.
Note: Preference group size shown here is the same as that returned through Bulk Volume Information Retrieval. By contrast, the preference group size displayed on the Cache Utilization page is the average of cache sizes sampled every 15 seconds, over a 15-minute period.
Defer Migrate (PG1) The total amount of cache defined using PG1. Any volumes assigned to Defer Migrate are a fraction of the Total Physical Used amount. Volumes in this group have preference to be retained in cache over other volumes. This group is only visible when the cluster possesses a physical library.
TS7720D Cluster Physical Used The amount of cache physically used for deduplication. This value does not include metadata. Physical Used cache is pinned, or, never removed from cache.
  Nominal Used The amount of cache space that would otherwise be used if deduplication were not employed. This value is used to determine the deduplication Capacity Ratio and does not include metadata.
  Capacity Ratio The ratio of Nominal Used to Physical Used cache capacity. This data set gives the amount of cache capacity improvement when deduplication is used.
TS7700 DS8000 Object Store   It will include the amount of object data stored in the object cache partition.