On Mon, Nov 20, 2017 at 05:25:16PM +0000, Giles Orr via talk wrote:
I ran a backup today and noticed one file because it took so long to back up. I'm using FC25 on this machine, and used the OS packages of Docker. I seem to have a 100G file on a 12G partition:
root@toshi7:/var/lib/docker/devicemapper/devicemapper# ls -lh total 34M -rw------- 1 root root 100G Oct 25 22:02 data -rw------- 1 root root 2.0G Oct 25 22:02 metadata root@toshi7:/var/lib/docker/devicemapper/devicemapper# df -h Filesystem Size Used Avail Use% Mounted on ... /dev/sda8 16G 12G 3.8G 75% / tmpfs 7.8G 776M 7.1G 10% /tmp /dev/mapper/home_crypt 237G 211G 24G 91% /home ...
/var/ is part of / , not a separate partition. The file appears to be a plain file, not a link or device. How exactly did my backup process (rsync to an external hard drive) manage to back up 100G of data from a 12G partition?
Probably a sparse file. Telling rsync to handle sparse files efficiently will help a lot. If you don't tell it, it will expand the sparse file with the unwritten parts being all zeros. Often disk images for VMs are sparse files (so unwritten parts are not actually allocated yet). -- Len Sorensen