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linux:snapshots

Overview of Backup system

Disk Backup

On disk every night a full backup of the home directory structure is stored on /disks/systembackup. This backup runs for a couple of hours for the current size of the home disk (1 TB). The copies can be accessed from the directory tree: /disks/systembackup. The backup disk scheme is rotated in a particular pattern:

Ident Interval Number kept
daily 24 hours 7
weekly 1 week 4
monthly 1 month 3

The most recent copy in the tree is named daily.0, the one before that is named daily.1. Every Monday the oldest daily copy, daily.6, will be renamed to weekly.0 and all older weekly.N copies are rotated to weekly.N+1 with the highest N=3.

A directory listing could yield:

drwxr-xr-x 3 root root 4096 Mar 13 23:34 daily.0

drwxr-xr-x  3 root root 4096 Mar 12 23:34 daily.1
drwxr-xr-x  3 root root 4096 Mar 11 23:34 daily.2
drwxr-xr-x  3 root root 4096 Mar 10 23:34 daily.3
drwxr-xr-x  3 root root 4096 Mar  9 23:34 daily.4
drwxr-xr-x  3 root root 4096 Mar  8 23:34 daily.5
drwxr-xr-x  3 root root 4096 Mar  7 23:34 daily.6
drwxr-xr-x  3 root root 4096 Feb 28 22:34 weekly.0
drwxr-xr-x  3 root root 4096 Feb 21 22:34 weekly.1
drwxr-xr-x  3 root root 4096 Feb 14 22:34 weekly.2
drwxr-xr-x  3 root root 4096 Feb  7 22:34 weekly.3

From the directory listing time stamps you can deduce the time at which the particular copy has been make and decide into which branch you have to traverse to retrieve the lost file.

You cannot write in this directory structure! It would mess up the scheme.

Filesystem snapshots

In addition, snapshots will also be made at filesystem level for important disks (e.g. software'', web site directories, etc). Recovering something from these locations involves a lot more work, and administrative privileges. ===== Backups of data ===== No central backups are made of user data. Only you as user will know which data is important, and how often it changes (imaginge us spending lots of time and money on weekly backups of data that hasn't been touched in years!). The best solution for personal backups is, to store a copy on another disk, either locally (e.g. copy from /data2 to /data1), on another computer (eg arrange with a co-worker to store eachothers' backup) or on an external usb-disk. External disks are quite cheap these days, so there is probably funding in your project to buy one.

linux/snapshots.txt · Last modified: 2015/05/21 10:34 (external edit)