Hi,
I've been struggling with something over the past days. I was creating backups of KVM virtual machines using '
virt-backup.pl' with plzip as the compression option (dd if=/dev/vg/logvol | plzip -c > img.lz).
The images are quite big as they're full disk dumps of a 100GB LVM logical volume.
Using plzip 0.9 from Ubuntu's 13.10 distribution.
When issuing:
# plzip -dc Archimedes_vda_2014-01-02_18-26-27.img.lz | dd of=/dev/vg/logvol1
, and starting the VM from the new logical volume, I get kernel panics (thrown by the guest) or odd grub behavior, such as:
error: file '/grub/i386-pc/normal.mod' not found.
or
error: attempt to read or write outside of partition
Entering rescue mode...
grub rescue>
.
However, when issuing:
# lzip -dc Archimedes_vda_2014-01-02_18-26-27.img.lz | dd of=/dev/vg/logvol1
, and starting the VM from the new logical volume, everything runs without a problem.
I've performed a few tests and it appears that plzip and lzip have different behavior when it comes down to decompression:
# plzip -vvdc Archimedes_vda_2014-01-02_18-26-27.img.lz | dd of=/lv/archi-plzip.img
Archimedes_vda_2014-01-02_18-26-27.img.lz:
10728352+0 records in
10728352+0 records out
5492916224 bytes (5.5 GB) copied, 118.74 s, 46.3 MB/s
# lzip -vvdc Archimedes_vda_2014-01-02_18-26-27.img.lz | dd of=/lv/archi-lzip.img
Archimedes_vda_2014-01-02_18-26-27.img.lz: version 1, dictionary size 8 MiB. done
Archimedes_vda_2014-01-02_18-26-27.img.lz: version 1, dictionary size 8 MiB. done
<snip>
Archimedes_vda_2014-01-02_18-26-27.img.lz: version 1, dictionary size 8 MiB. done
Archimedes_vda_2014-01-02_18-26-27.img.lz: version 1, dictionary size 8 MiB. done
Archimedes_vda_2014-01-02_18-26-27.img.lz: version 1, dictionary size 8 MiB. done
209715200+0 records in
209715200+0 records out
107374182400 bytes (107 GB) copied, 2034.86 s, 52.8 MB/s
# md5sum *.img
2ee1b13b009dc0c739a442e1e72ce690 archi-plzip.img
4f7547e1c43e2fdf3d90d980867245ff archi-lzip.img
# ls -la
total 110221816
drwxr-xr-x 3 root root 4096 Jan 5 11:20 .
drwxr-xr-x 23 root root 4096 Jan 5 11:14 ..
-rw-r--r-- 1 root root 5492916224 Jan 5 11:18 archi-plzip.img
-rw-r--r-- 1 root root 107374182400 Jan 5 11:54 archi-lzip.img
drwx------ 2 root root 16384 Jan 5 11:15 lost+found
#
Next to the uncompressed size difference, also notice that the verbose output is different.
The version of lzip in Ubuntu 13.10 is 1.14 (vs. 0.9 for plzip). Is this the root cause of the issue I'm experiencing? As I couldn't find change logs.
Any plans to update plzip and to update the Ubuntu package?
Thanks,
Filip