[linux-lvm] lvcreate --thin gives "unknown segment type" error
zkabelac at redhat.com
Mon Jul 22 20:18:48 UTC 2013
Dne 22.7.2013 13:23, Kumar amit mehta napsal(a):
> On Mon, Jul 22, 2013 at 06:57:42AM -0400, Kumar amit mehta wrote:
>> On Mon, Jul 22, 2013 at 02:15:36PM +0200, Zdenek Kabelac wrote:
>>> configure --with-thin=internal
>>> (and you will likely miss '--enable-udev_sync'
>> Thank you, it worked!
>> However, It seems that "discards" behavior for thin pool is not
>> supported on RHEL 6.4. Please confirm.
>> # ./configure --with-thin=internal --enable-debug
>> # make; make install
>> # lvcreate --discards passdown -L 1G -T thinvg1/thinlv1
>> Logical volume "thinlv1" created
>> # lvs -o +devices|grep -i thinlv1
>> thinlv1 thinvg1 twi-a-tz- 1.00g 0.00
>> # dmesg
>> device-mapper: thin: Data device (dm-3) discard unsupported: Disabling
>> discard passdown.
It's your backend device used for thinpool data which doesn't support
discard. So it fallbacks to nopassdown behaviour (discard is processed only
at pool level).
> I'm invoking these commands on a VM. I do not know, from where these
> storage were mapped to my VM(were done my some storage admin). However
Important piece of puzzle - if you want to see TRIM command hits your storage,
your storage needs to support it ;)
BTW it's perfectly ok to use thin pool only with nopassdown.
NOTE: issue_discard in lvm.conf is not related in any way with --discards
option for thin pool creation.
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