lvm-autosnap

Introduction

lvm-autosnap takes and maintains a periodic series of lvm snapshots for an arbitrary logical volume ##

About

Yet another BASH script to take lvm snapshots? Yes, indeed, but it's written to try to overcome the fragility of a script that parses command line output then breaks in weird and wonderful ways. So, instead of messing around with parsing dates and trying to do maths in BASH, we simply ask lvm to do it for us. Shocking eh?

The other big difference is that although the snapshots are dated using an ISO-86-1 format, it's the metadata creation date that is used for processing, not the filename. The advantage here is that one can rename the snapshots if desired, yet they will still process as normal.

A further difference is that lvm-autosnap snapshots are identified by a metadata tag, causing lvm-autosnap to be immune from filename changes. Thus, one can simply remove the tag lvchange --deltag autosnap <vg>/<snapshot> to allow the snapshot to remain, if needed, for posterity. Likewise, a tag can be added to a snapshot lvchange --addtag autosnap <vg>/<snapshot> to add it to the pool of snapshots considered by lvm-autosnap.

Usage

lvm-autosnap --vg=<vg> --lv=<lv> [optional parameters]

Required parameters

• -g | --vg

  The logical volume group

• -l | --lv

  The logical volume name

Optional parameters

• -h | --help

  Hi there!

• -d | --dry-run

  List commands, do not commit changes

• -k | --keep-time

  Retention period in "keep-units". Default=days

• -m | --max-daily

  Maximum number of snaphots allowed per day, Default=5

• -s | --size

  Snapshot size. default=2G

• -t | --tag

  Tag to be applied to snapshots. Default=autosnap

• -u | --keep-units

  Retention period (see keep-units). Default=8

Examples

• lvm-autosnap --vg=mv_vg --lv=my_lv

  take an autosnap of mv_vg/my_lv, prune using the default retention period of 8 days

• lvm-autosnap --vg=mv_vg --lv=my_lv --size=4G

  take a 4G autosnap of mv_vg/my_lv, prune using the default retention period of 8 days

• lvm-autosnap --dry-run --vg=mv_vg --lv=my_lv --keep-time=1 --keep_units=hour

  SIMULATE an autosnap of mv_vg/my_lv, with pruning of other autosnaps older than one hour

Installation

• Copy the lvm-autosnap executable to the directory of your choice.
  • cp lvm-autosnap /usr/local/sbin/.
• Make it executable
  • chmod 755 /usr/loca/sbin/lvm-autosnap
• Copy and amend the setting for logrotate and cron
  • cp etc/logrotate.d/lvm-autosnap /etc/logrotate.d/.
  • cp etc/cron.daily/lvm-autosnap /etc/cron.daily/.
• Additionally, pay attention to the follow settings in /etc/lvm/lvm.conf
  • snapshot_autoextend_threshold
  • snapshot_autoextend_percent
  • thin_pool_autoextend_threshold
  • thin_pool_autoextend_percent

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Have fun -- aj