[linux-lvm] Does LVM RAID1 have TRIM support?

[Jarkko Oranen]

Hello

Yesterday I experimented a bit with my RAID configuration on a pair of
SSDs, and it seems that LVM's native RAID does not have TRIM support...
At least, when I try to run fstrim manually, it complains even though
issue_discards is enabled. Plain LVs on top of an MD RAID PV do work, of
course.

Am I perhaps missing some configuration, or do RAID1 logical volumes
simply not have support for TRIM yet? I'm running a fairly recent kernel
(3.15.8) and lvm version says this:

  LVM version:     2.02.106(2) (2014-04-10)
  Library version: 1.02.85 (2014-04-10)
  Driver version:  4.27.0

As an aside, can anyone point me to documentation or other resources
about the pros and cons of LVM native RAID1 setup (which I understand
uses MD RAID internally?) vs. MD RAID PV + LVM. It seems I might be able
to save some SSD space and only mirror the LVs I actually need to keep
safe from crashes.

--
Jarkko Oranen