[linux-lvm] Unable to un-cache logical volume when chunk size is over 1MiB

Ryan Launchbury ryan at magenta.tv
Mon Jun 25 17:20:54 UTC 2018

Hi Gionatan,

The system with the issue is with  writeback cache mode enabled.

Best regards,


On Mon, 25 Jun 2018, 18:19 Gionatan Danti, <g.danti at assyoma.it> wrote:

> Il 24-06-2018 21:18 Ryan Launchbury ha scritto:
> > In testing, forcibly removing the cache, via editing the LVM config
> > file has caused extensive XFS filesystem corruption, even when backing
> > up the metadata first and restoring after the cache device is missing.
> > Any advice on how to safely uncache the volume would be massively
> > appreciated.
> It is my understanding that a writethrough cache should *never* have any
> data that are not on the backing volumes already.
> In other words, forcibly removing a writethough cache (ie: disconnetting
> the physical cache device) should not cause any harms to
> filesystem/data.
> Can you show the output of "dmsetup table"?
> Thanks.
> --
> Danti Gionatan
> Supporto Tecnico
> Assyoma S.r.l. - www.assyoma.it
> email: g.danti at assyoma.it - info at assyoma.it
> GPG public key ID: FF5F32A8
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