Copy Linux sparse files over network · uwot.eu
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Copy Linux sparse files over network

· by fabio · Read in about 1 min · (147 Words)
linux qcow2 Qemu sparse file

Sparse files are nice to use to store virtual machine’s virtual disks but can be a real pain in the ass to backup efficiently, especially over the network.
Luckily rsync provides a way to intelligently copy sparse files both locally and over the network.
The trick is use –sparse and –inplace options.
Let’s say we have a sparse 60 GB qemu virtual disk with only around 7 GB used:

$ ls -lh fedora24.qcow2 
-rw------- 1 root root 61G Nov  8 19:11 fedora24.qcow2
$ du -h fedora24.qcow2 
7.2G    fedora24.qcow2

The first thing to note is that ls does not recognize sparse files while du does.
The first time a file is copied use the –sparse option:

$ rsync -avP --sparse fedora24.qcow2 root@remotemachine:/tmp

Every other time use –inplace to tell rsync to copy only the blocks that actually changed since the last copy:

$ rsync -avP --inplace fedora24.qcow2 root@remotemachine:/tmp