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From: Brassow Jonathan <jbrassow@redhat.com>
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Date: Tue, 23 Sep 2014 23:17:42 -0500
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Subject: Re: [linux-lvm] Does LVM RAID1 have TRIM support?
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On Sep 12, 2014, at 2:24 AM, Jarkko Oranen wrote:

> On Thu, 2014-09-11 at 18:31 -0500, Brassow Jonathan wrote:
> 
>> dm-raid.c does not have that - dm-raid1.c does.  dm-raid1.c is a mirroring implementation specific to device-mapper.  It is used by LVM for pvmove functionality (and is otherwise being slowly phased out).  dm-raid.c is the device-mapper wrapper around the MD RAID personalities.  It does not have discard support.
>> 
>> I will ask Neil what the current state of discard support is in MD.  I see that "support" was added in Oct of 2012 (starting at commit 2ff8cc2), but I remember them having problems with discards + any resync operations.  If Neil says it is ok, I will turn it on.
>> 
> 
> In the code that I'm looking at dm-raid.c definitely sets
> num_discard_bios to 1 on something... As does dm-raid1.c. However,
> Thanks for looking into it!

Heinz Mauelshagen is looking to get this included upstream now.  Thanks for the poke!  :)

Initial status query:
http://marc.info/?l=linux-raid&m=141047869821032&w=2

Patch posted for consideration:
https://www.redhat.com/archives/dm-devel/2014-September/msg00126.html

 brassow