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Chris Gerhard's Weblog
Sunday November 20, 2005
Snapping every minute I'm not sure when ZFS was being designed it's target was going to be laptops. However on mine it is looking great. So good I upgraded my Dell this afternoon.
A short script and I have a snapshot every minute which I can keep for an hour and then the hourly snaphshots kept for a day. The daily snapshots kept for a month and the monthly snaphosts kept for a year.
It will be ineteresting to see how the disk space usage works out over the longer term. This all comes from this script:
#!/bin/ksh -p
function take_snap
{
if zfs list -H -o name $1 >/dev/null 2>&1
then
zfs destroy $1
fi
zfs snapshot ${1}
}
case ${1:-boot} in
"boot")
snap=$(date '+%F-%T')
;;
"minute")
snap=minute_$(date +%M)
;;
"hour")
snap=hour_$(date +%H)
;;
"day")
snap=day_$(date +%e)
;;
"month")
snap=month_$(date +%m)
;;
esac
for fs in $(zfs list -H -o name -t filesystem)
do
take_snap ${fs}@${snap}
done
And this entry in cron:
* * * * * /export/home/local/snapshot minute 0 * * * * /export/home/local/snapshot hour 1 1 * * * /export/home/local/snapshot day 2 1 1 * * /export/home/local/snapshot month
All those snapshots:
: sigma IA 9 $; ls ~/.zfs/snapshot/ 2005-11-20-17:00:26 minute_20 minute_46 hour_21 minute_34 minute_47 hour_22 minute_35 minute_48 minute_00 minute_36 minute_49 minute_11 minute_37 minute_50 minute_12 minute_38 minute_51 minute_13 minute_39 minute_52 minute_14 minute_40 minute_53 minute_15 minute_41 minute_54 minute_16 minute_42 minute_55 minute_17 minute_43 minute_56 minute_18 minute_44 minute_57 minute_19 minute_45 : sigma IA 10 $;
listing out the snapshots it really does seem that they are free:
# zfs list | grep cjg home/cjg 33.0M 8.52G 30.5M /export/home/cjg home/cjg@2005-11-20-17:00:26 30.5K - 29.4M - home/cjg@hour_21 296K - 30.6M - home/cjg@minute_34 42.0K - 31.0M - home/cjg@minute_35 22.0K - 31.0M - home/cjg@minute_36 50.5K - 31.0M - home/cjg@minute_37 37.0K - 31.0M - home/cjg@minute_38 0 - 31.0M - home/cjg@minute_39 0 - 31.0M - home/cjg@minute_40 0 - 31.0M - home/cjg@minute_41 0 - 31.0M - home/cjg@minute_42 6.00K - 31.0M - home/cjg@minute_43 68.0K - 31.0M - home/cjg@minute_44 31.5K - 31.0M - home/cjg@minute_45 37.5K - 31.0M - home/cjg@minute_46 0 - 31.0M - home/cjg@minute_47 0 - 31.0M - home/cjg@minute_48 0 - 31.0M - home/cjg@minute_49 0 - 31.0M - home/cjg@minute_50 0 - 30.3M - home/cjg@minute_51 0 - 30.3M - home/cjg@minute_52 0 - 30.3M - home/cjg@minute_53 0 - 30.3M - home/cjg@minute_54 0 - 30.3M - home/cjg@minute_55 0 - 30.3M - home/cjg@minute_56 0 - 30.3M - home/cjg@minute_57 0 - 30.3M - home/cjg@hour_22 0 - 30.4M - home/cjg@minute_00 0 - 30.4M - home/cjg@minute_11 0 - 30.5M - home/cjg@minute_12 0 - 30.5M - home/cjg@minute_13 0 - 30.5M - home/cjg@minute_14 0 - 30.5M - home/cjg@minute_15 0 - 30.5M - home/cjg@minute_16 0 - 30.5M - home/cjg@minute_17 0 - 30.5M - home/cjg@minute_18 0 - 30.5M - home/cjg@minute_19 0 - 30.5M - home/cjg@minute_20 0 - 30.5M - home/cjg@minute_21 0 - 30.5M - home/cjg@minute_22 0 - 30.5M - home/cjg@minute_23 0 - 30.5M - #
I can feel an open letter to the admin of my home directory server comming along the lines of:
I want a snapshot every minute and I want it now.
( Nov 20 2005, 10:25:21 PM GMT ) Permalink Trackback
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No need for that letter Chris. As soon as our 'new' storage arrives we will be using Nevada and ZFS.
Posted by Paul Humphreys on November 21, 2005 at 08:37 AM GMT #
I hope it arrives soon, very soon.
Posted by Chris Gerhard on November 21, 2005 at 12:23 PM GMT #
Posted by Peter Baer Galvin on January 07, 2006 at 04:26 PM GMT #
Thanks for the bug fix. Feel free to publish the script more widely.
Posted by Chris Gerhard on January 07, 2006 at 10:20 PM GMT #
$ cat /etc/rc3.d/S99take.snapshot #!/sbin/sh # ident "@(#)take-snapshot 1.0 07/10/21 dbryant" # Could use some more sanity checking here... [ ! -d /usr/bin ] && exit [ ! -d /root/bin ] && exit # Take a snapshot at boot time SCRIPT="/root/bin/snapshot.ksh" case "$1" in 'start') if [ -x ${SCRIPT} ]; then ${SCRIPT} boot else echo "$0 failed to find ${SCRIPT} at boot." | /usr/bin/mailx -s root fi ;; *) echo "Usage: $0 { start }" exit 1 ;; esac exit 0 # EOFYour method has a nice "automatic" retention feature. But I like the idea of using unformatted dates such as "date +%Y%m%d%H%M". Since this allows for easier incremental transfers (think zfs send -i), and "date based" math (blow away everything older than N days|hours|minutes). Keep up the good work! DavidPosted by David Bryant on January 15, 2007 at 03:22 AM GMT #
RC scripts are so yesterday!;-). SMF is what you want.
I have moved on since this take a look at this blog entry http://blogs.sun.com/chrisg/entry/snapshot_on_boot
Then I have been taking the snapshots via samba and using a more descriptive name which I have carried over into the current version of the snapshot script. See http://blogs.sun.com/chrisg/entry/samba_meets_zfs.
Finally I have a clean up script that runs to delete the old snapshots: http://blogs.sun.com/chrisg/entry/a_faster_zfs_snapshot_massacre.
Posted by Chris Gerhard on January 15, 2007 at 03:49 PM GMT #