[Users] OpenVZ and ZFS excellent experience

[Scott Dowdle]

Greetings,

----- Original Message -----
> And I checked my containers with 200% disk overuse from first message
> and got negative result. 24Gb of wasted space is not related with
> cluster size issue.

Yeah, but 24GB is a long way off from your original claim (if I remember correctly) of about 900GB... but those probably aren't comparing the same things anyway.

I'm lost... because ploop and zfs are not, so far as I can tell, competing filesystems on the same level.  zfs is competes with other filesystems like ext4 or xfs... whereas for OpenVZ, so far as I know, there isn't a disk-file-as-disk competitor.  Given the popularity and stability of the current qcow2 format popularized by KVM/qemu... and the large number of tools compatible with qcow2 (see libguestfs)... I'm wondering if it would be valuable to add qcow2 support to OpenVZ?

You are currently using zfs with OpenVZ, correct?  And you didn't have to modify any of the OpenVZ tools in order to do so, correct?  If that is the case, what is it you want from the OpenVZ project with regards to zfs?

So far as I'm concerned the license incompatiblity with the zfs/openzfs makes it where it can not be distributed with stuff licensed under the GPL... so I don't really see a way for OpenVZ to ever ship a zfs-enabled kernel... but yeah, if needed they could add support for it in the tools if that makes sense.  I'm unclear on what you are looking for other than turning the OpenVZ mailing list into a zfs advocacy group.

I do however appreciate you metering wasted disk space by ploop as additional data the OpenVZ devs can work with but as long as ploop isn't using more disk space than the max size of the container disk, I don't really see a problem.  While it means one can't over-subscribe the physical disk as much... excessive over-subscription is not ideal either... with wasted space acting as a sort of pre-allocation buffer... and not actually wasted unless the container's disk isn't going to grow in the future.

I'd also like to see a comparison between ploop wasted space and that of qcow2... although I'm not sure that qcow2 offers compaction features... since I don't find the word compact in the qemu-img man page.  Maybe there is a separate tool for qcow2?

TYL,
-- 
Scott Dowdle
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