[linux-lvm] thin discards

[Raymond Jennings]

Do snapshots behave the same way as thin volumes wrt discards?


On Sun, Jul 21, 2013 at 3:47 AM, Zdenek Kabelac <zkabelac at redhat.com> wrote:

> Dne 21.7.2013 09:10, Raymond Jennings napsal(a):
>
>  So can thin volumes support discards independently of the device
>> underneath them?
>>
>> I expected fstrim to free space in the thin pool.
>>
>
> Yes - you are expecting it correctly.
>
> Ignore is mostly usable in case you do not want to free already
> provisioned space - which might be in certain cases better for performance.
>
> But you need to use recent enough kernels and lvm2 tools - since discards
> support required kernel updates.
>

Kernel: 3.10.1-gento
LVM2:  2.02.97

Are these versions recent enough?

Upstream has this:
>
> passdown   TRIM ->  thin-vol -> thin-pool -> PV
> (if the PV doesn't support discard - you get kernel report error report
> and it fallbacks to nopassdown behaviour)
>
> nopassdown TRIM ->  thin-vol -> thin-pool
>
> ignore     TRIM ->  thin-vol
>
>
>
> Zdenek
>
>
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