A Disk-Only TS7700 Engine does not attach to a physical backend library; all virtual volumes are stored in the cache. When the available free cache space is less than 3 TB, the cluster enters the Limited Free Space Cache Warning state. In this state, mounts and host I/O transfers will continue to be accepted for a time. However, unless some older data is removed, the library will soon run out of cache resources and mounts will no longer be accepted. The cluster exits this state when the available free cache space is more than 3.5 TB. If the cluster is in a grid configuration, the Limited Free Space Cache Warning state reflects the composite state of cache in all TS7700 Disk-Only Clusters in the grid.