[linux-lvm] LVM cache/dm-cache questions.

Brassow Jonathan jbrassow at redhat.com
Mon Jun 20 16:27:17 UTC 2016

> On Jun 11, 2016, at 7:36 PM, sergei <sergei.franco at gmail.com> wrote:
> Hi,
> I have a few simple questions regarding relatively new feature LVM cache/dm-cache.
> From second hand information on internet, it appears that you cannot resize cached volume.
> Please correct me if I am wrong: to resize a cached volume, one needs to lvremove the cache, resize and recreate the cache?

This is true at the moment.  You are likely to be able to simply resize online in the future.

> In scenario where cache device fails, how safe is the data on the cached LVM?

If you are using writethrough, quite safe.  If you are using ‘writeback’, probably not (RAID for your cache in this case would probably be wise).

> Is it possible to make snapshots of the cached device?

easy answer is “no”.

complicated answer includes a ‘yes’.  You can cache a poolDataLV, then your thinLV and all its thinSnaps would be cached.


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