On 29/04/2016 10:44, Marek Podmaka wrote:
Hello Xen,
Now I'm not sure what your use-case for thin pools is.
I don't see it much useful if the presented space is smaller than
available physical space. In that case I can just use plain LVM with
PV/VG/LV. For snaphosts you don't care much as if the snapshot
overfills, it just becomes invalid, but won't influence the original
LV.
Let me add one important use case: have fast, flexible snapshots.
In the past I used classic LVM to build our virtualization servers, but
this means I was basically forced to use a separate volume for each VM:
using a single big volume and filesystem for all the VMs means that,
while snapshotting it for backup purpose, I/O become VERY slow on ALL
virtual machines.
On the other hand, thin pools provide much faster snapshots. On the
latest builds, I begin using a single large thin volume, on top of a
single large thin pool, to host a single filesystem that can be
snapshotted with no big slowdown on the I/O part.
I understand that it is a tradeoff - classic LVM mostly provides
contiguous blocks, so fragmentation remain quite low, while thin
pools/volumes are much more prone to fragament, but with large enough
chunks it is not such a big problem.
Regards.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8
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