I’ve made a test to find the best “compressed” solution for thin provisioning on virtual machines.
f18.qcow2 is a default minimal Fedora 18 installation.
$ qemu-img info f18.qcow2
image: f18.qcow2
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 1.1G
cluster_size: 65536
Below is the result, sorted by size
1170252 f18.qcow2
746188 f18.qcow2.spars
253552 f18.qcow2.spars.compressed
236860 f18.qcow2.spars.compressed.lrz
236076 f18.qcow2.spars.compressed.xz
151028 f18.qcow2.xz
146172 f18.qcow2.spars.xz
141276 f18.qcow2.spars.lrz
141048 f18.qcow2.lrz
It seems that Con Kolivas has made an extraordinary work with lrzip
And these are the commands i’ve run (sorted by the result of above output):
| f18.qcow2 | qemu-kvm f18.qcow2 -cdrom Fedora-18-x86_64-netinst.iso -cpu host -usbdevice tablet -m 2048 |
| f18.qcow2.spars | virt-sparsify f18.qcow2 f18.qcow2.spars |
| f18.qcow2.spars.compressed | virt-sparsify - -compress f18.qcow2 f18.qcow2.spars.compressed |
| f18.qcow2.spars.compressed.lrz | lrzip f18.qcow2.spars.compressed |
| f18.qcow2.spars.compressed.xz | xz -k f18.qcow2.spars.compressed |
| f18.qcow2.xz | xz -k f18.qcow2 |
| f18.qcow2.spars.xz | xz -k f18.qcow2.spars |
| f18.qcow2.spars.lrz | lrzip f18.qcow2.spars |
| f18.qcow2.lrz | lrzip f18.qcow2 |
My specs are:
$ grep 'model name' /proc/cpuinfo | head -1
model name : Intel(R) Core(TM) i7-3517U CPU @ 1.90GHz
$ grep -c processor /proc/cpuinfo
4
$ grep MemTotal /proc/meminfo
MemTotal: 8038060 kB
I am using LVM for storage to virtual machines.
One simply way to make backups (even if the machine is online) is through dd.
(but if you are using a database, online is out of question).
dd will backup the entire partition to a raw image.
Lets make an example:
# time dd if=/dev/vg01/winxp of=winxp.img bs=1024
5242880+0 records in
5242880+0 records out
5368709120 bytes (5,4 GB) copied, 111,164 s, 48,3 MB/s
So we have a 5Gb backup raw image with sparse files into.
If only there was a way to remove sparse files to reduce the size!
Wait … it does exist: virt-sparsify
# virt-sparsify winxp.img winxp.img.spars
...
Sparsify operation completed with no errors. Before deleting the old
disk, carefully check that the target disk boots and works correctly.
# ls -ltr
-rw-r--r-- 1 root root 5368709120 Αύγ 28 11:55 winxp.img
-rw-r--r-- 1 root root 5368709120 Αύγ 28 11:59 winxp.img.spars
# du -h *
5,1G winxp.img
3,1G winxp.img.spars
2gb sparse files have just removed !
Now you can compress the backup image to reduce the size even more:
# du -h winxp.img*
5,1G winxp.img
3,1G winxp.img.spars
1,4G winxp.img.spars.lrz
We can now remove winxp.img & winxp.img.spars (8.2Gb) from our backup storage.