Description

The user should have the ability to issue a command to 'thin-provision'ed volumes that issues discards for unused space.  This should be able to be done online.

Zdenek Kabelac's initial thoughts on this feature can be found in this document.

There are a number of reasons this feature is desirable:

• Having discards on continuously can degrade performance
• Deleted files may free up blocks, but not entire thin "chunks", thus, the discard cannot be issued.  Waiting for these events to accumulate can allow for more chunks to be freed vs impotent discards.
• A thin_trim can be run when thin volumes are removed, which is out-of-band for normal I/O operations.
• A thin_trim can be run in response to events, like high-water thresholds (i.e. running out of physical space)

What SSTs and Layered Product teams should review this?

• Logical Storage