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vzstats in beta

For the last two weeks or so we've been working on vzstats -- a way to get some statistics about OpenVZ usage. The system consists of a server, deployed to http://stats.openvz.org/, and clients installed onto OpenVZ machines (hardware nodes). This is currently in beta testing, with 71 servers participating at the moment. If you want to participate, read http://openvz.org/vzstats and run yum install vzstats on your OpenVZ boxes.

So far we have some interesting results. We are not sure how representative they are -- probably they aren't, much more servers are needed to participate-- but nevertheless they are interested. Let's share a few preliminary findings.

First, it looks like almost no one is using 32-bits on the host system anymore. This is reasonable and expected. Indeed, who needs system limited to 4GB of RAM nowdays?

Second, many hosts stay on latest stable RHEL6-based OpenVZ kernel. This is pretty good and above our expectations.

Third, very few run ploop-based containers. We don't understand why. Maybe we should write more about features you get from ploop, such as instant snapshots and improved live migration.

Comments

early_morning
Apr. 30th, 2013 03:33 am (UTC)
Wow, thanks! For some reason I thought ploop is more like KVM or vmware disk images where you had to deal with partition resize headaches, etc. But then how do you deal with image fragmentation? What happens when I downsize a heavily fragmented container?

I guess I will just need to experiment with this to better understand how it works.

But there is one more issue... Currently, for backups, we rsync the entire /vz/private folder to a remote location. This not only allows us to save i/o (we only need to copy changed files), but also perform differential backups and save tons of disk space on the backup server. I always assumed this becomes impossible with ploop. Am I missing anything here?
k001
May. 3rd, 2013 01:37 am (UTC)
With ploop, you can make consistent backups using ploop snapshot feature. See http://wiki.openvz.org/images/f/f3/Ct_in_a_file.pdf presentation, a section about snapshots and backups.

Basically, a backup is:
- create snapshot
- copy this snapshot
- merge this snapshot down

If you don't do merge, you can have real differential backups, just by copying the next snapshot.

Also, see vzctl man page (http://wiki.openvz.org/Man/vzctl.8#Snapshotting) on available snapshot commands. In addition,
vzctl 4.3 will add snapshot-mount and snapshot-umount commands.

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