[linux-lvm] Snapshot behavior on classic LVM vs ThinLVM

[Gionatan Danti]

Il 07-04-2017 10:19 Mark Mielke ha scritto:
> 
> I found classic LVM snapshots to suffer terrible performance. I
> switched to BTRFS as a result, until LVM thin pools became a real
> thing, and I happily switched back.

So you are now on lvmthin? Can I ask on what pool/volume/filesystem 
size?

> 
> I expect this depends on exactly what access patterns you have, how
> many accesses will happen during the time the snapshot is held, and
> whether you are using spindles or flash. Still, even with some attempt
> to be objective and critical... I think I would basically never use
> classic LVM snapshots for any purpose, ever.
> 

Sure, but for nightly backups reduced performance should not be a 
problem. Moreover, increasing snapshot chunk size (eg: from default 4K 
to 64K) gives much faster write performance.

I more concerned about lenghtly snapshot activation due to a big, linear 
CoW table that must be read completely...

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Danti Gionatan
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