[linux-lvm] [dm-devel] do not disable ext4 discards on first discard failure? [was: Re: dm snapshot: ignore discards issued to the snapshot-origin target]

Lukas Czerner lczerner at redhat.com
Mon May 2 14:39:31 UTC 2011

On Mon, 2 May 2011, Martin K. Petersen wrote:

> >>>>> "Lukas" == Lukas Czerner <lczerner at redhat.com> writes:
> Lukas> So I gave it a try. First of all the device composed of SSD and
> Lukas> spinning disk does export discard_support information properly,
> Lukas> however it also advertise discard_zeroes_data which is wrong and
> Lukas> possibly dangerous and should be fixed!
> I can't reproduce this here. If I mix discard and non-discard devices
> things work correctly. discard_zeroes_data also gets cleared if I mix
> discard-capable drives where one zeroes and one doesn't.

[root at trim ~]# hdparm -I /dev/sdb | grep -i trim
[root at trim ~]# cat /sys/block/sdb/queue/discard_zeroes_data
[root at trim ~]# hdparm -I /dev/sdd | grep -i trim
           *    Data Set Management TRIM supported
           *    Deterministic read after TRIM
[root at trim ~]# cat /sys/block/sdd/queue/discard_zeroes_data 
[root at trim ~]# pvcreate /dev/sdd1 
  Physical volume "/dev/sdd1" successfully created
[root at trim ~]# pvcreate /dev/sdb3 
  Physical volume "/dev/sdb3" successfully created
[root at trim ~]# vgcreate vg_test /dev/sdd1 /dev/sdb3 
  Volume group "vg_test" successfully created
[root at trim ~]# lvcreate -L 3500M vg_test
  Logical volume "lvol0" created
[root at trim ~]# ls -lah /dev/mapper/vg_test-lvol0 
lrwxrwxrwx. 1 root root 7  2. kvě 10.30 /dev/mapper/vg_test-lvol0 -> ../dm-0
[root at trim ~]# cat /sys/block/dm-0/queue/discard_zeroes_data 
[root at trim ~]# uname -r
[root at trim ~]# cat /proc/partitions
   8       19    1951897 sdb3
   8       49    1951866 sdd1
 253        0    3584000 dm-0

So I assume it got fixes just recently ?. I'll give it a try with the
up-to-date kernel.


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