On Wed, Oct 19 2011 at 10:09am -0400, Yann Droneaud <yann@droneaud.fr> wrote: > Le mercredi 19 octobre 2011 à 12:45 +0200, Yann Droneaud a écrit : > > Hi, > > > > Does lvremove, vgremove, pvremove issue discard (eg. TRIM) commands > > in order to release LE/PE/metadata blocks from the underlying devices (SSD) ? > > > > It seems the discard feature was added to LVM2 since version 2.02.85 > (released on 29th April 2011), in WHATS_NEW: > > Add "devices/issue_discards" to lvm.conf. > Issue discards on lvremove and lvreduce etc. if enabled and supported. > > But the documentation is unclear about it. In example.conf.in / > lvm.conf.5.in: > > " > Issue discards to a logical volumes's underlying physical volume(s) when > the logical volume is no longer using the physical volumes' space (e.g. > lvremove, lvreduce, etc). Discards inform the storage that a region is > no longer in use. Storage that supports discards advertise the protocol > specific way discards should be issued by the kernel (TRIM, UNMAP, or > WRITE SAME with UNMAP bit set). Not all storage will support or benefit > from discards but SSDs and thinly provisioned LUNs generally do. If set > to 1, discards will only be issued if both the storage and kernel > provide support. > " > > > Does it apply for the blocks holding meta data, > e.g. will pvremove issue discard requests for the PV meta data ? The discards are only issued for the physical extents that were used in a volume's data area. PV metadata isn't discarded, and really there would be little benefit to doing so. _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
