Hello,
2012/8/7 Bastian Friedrich <bastian.friedr...@collax.com>
> Am Montag, 6. August 2012, 20:35:52 schrieb Radosław Korzeniewski:
> > If a user will have a thin-provisioned volume that he can successfully
> use
> > sparse=yes option without any garbage and can use it even with a vm
> image.
>
> I'm not sure whether I understand correctly what you are writing; however,
> I
> suppose you are still at risk of data corruption.
>
> If you have a VM running on an LV, and you have a _file_ inside that VM
> that
> contains large chunks of zeros, these zeros are indistinguishable from
> "empty"
> blocks. Thus, during restore, the respective blocks are not written,
> (possibly) resulting in garbage on disk -- and thus garbage in said file of
> the VM.
>
No, this is not correct if you have a thin-provisioned lvm volumes/disks.
It works like a sparse file on fs. If you don't write any data to the part
of the volume/disk then this part of the volume/disk is not allocated on
backed storage. So, when you read previously unwritten data then you'll get
an empty(zeros) data block.
Standard lvm volumes are not thin-provisioned and you allocate all data
blocks up to the size of the volume. This is a main problem where garbage
comes from.
Best regards
--
Radosław Korzeniewski
rados...@korzeniewski.net
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