Because I (taggart) keep forgetting, I am creating this page to track the details about TRIM / DISCARD support.
DISCARD support for dmcrypt was added to Linux in 3.1.
Support in the dmcrypt tools was added in 1.4.x
The linux commit
commit 772ae5f54d69c38a5e3c4352c5fdbdaff141af21
Author: Milan Broz <mbroz@redhat.com>
Date: Tue Aug 2 12:32:08 2011 +0100
dm crypt: optionally support discard requests
Add optional parameter field to dmcrypt table and support
"allow_discards" option.
Discard requests bypass crypt queue processing. Bio is simple remapped
to underlying device.
Note that discard will be never enabled by default because of security
consequences. It is up to the administrator to enable it for encrypted
devices.
(Note that userspace cryptsetup does not understand new optional
parameters yet. Support for this will come later. Until then, you
should use 'dmsetup' to enable and disable this.)
- page detailing the implications of enabling TRIM on a dmcrypt device (by the author of the above commit)
- How to enable it
- some howtos
