Shadow Copies with Snapshots

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Revision as of 01:24, 10 October 2016 by Jasonblewis (talk | contribs) (typo)

The base Samba-Configuration is quite simple, therefore you can easily follow the instructions of the Official HowTo.

The tricky part is the management of the snapshots.

But before you read on, a little warning:

Some people have the idea that the could have snapshots for the last 30 days and four different volumes and maybe twice a day, all in all 240 snapshots. That's not possible - you shouldn't have more than 15 snapshots at a time (and that's quite a lot, actually I think there is a bug in lvm2 reported and numbers above 16 snapshots may mess up your volumes).
You have to check the change rate of your data before you plan your snapshots, otherwise your volume groups may be quickly out of space. Also keep in mind, that your disks have more work to do the more snapshots they have to care about.
The environments, I wrote this script for, have one volume, size about 20GB and a changerate of 100MB per day and maybe 500MB in two weeks.

Now to the subject:

After planing how many snapshots of which volumes you need, all you have to do is to place this Shadow Copies with Snapshots Script in a useful place (e.g. /usr/local/sbin/), place some entries in your crontab and create a configuration file (if you use an other place than /etc/samba/smbsnap.conf you have to change the path in the script).
Before this script is ready to work, the kernel-module dm_snapshot has to be loaded and if your volumes are loaded at boot time (i.e. /etc/fstab), this has to be done in your initrd.
Read the head of the script for more detailed documentation and a configuration example.