Support for caching thinly-provisioned logical volumes with limitations
Red Hat Enterprise Linux 7.3 provides the ability to cache thinly provisioned logical volumes.
This brings caching benefits to all the thin logical volumes associated with a
particular thin pool. However, when thin pools are set up in this way, it is not currently possible to grow the thin pool without removing the cache layer first. This also means that thin pool auto-grow features are unavailable. Users should take care to monitor the fullness and consumption rate of their thin pools to avoid running out of space. Refer to the lvmthin(7) man page for information on thinly-provisioned logical volume and the lvmcache(7) man page for information on LVM cache volumes.
Thin-pools are normally capable of auto-growing as they become full - preventing more serious issues when a pool completely fills. This ability is unavailable when there is a cache layer on top of the ThinDataLV. Users must be notified of this limitation via a release note.
Closing this bug now that the proper documentation is in the release notes.