Big vote for cron jobs.
Our snapshot are created by a script, installed on each GPFS node. The script
handles naming, removing old snapshots, checking that sufficient disk space
exists before creating a snapshot,
etc. We do snapshots every 15 minutes, keeping them with lower frequency over
longer intervals. For example:
current hour: keep 4 snapshots
hours -2 .. -8 keep 3 snapshots per hour
hours -8 .. -24 keep 2 snapshots per hour
days -1 .. -5 keep 1 snapshot per hour
days -5 .. -15 keep 4 snapshots per day
days -15 .. -30 keep 1 snapshot per day
the duration & frequency & minimum disk space can be adjusted per-filesystem.
The automation is done through a cronjob that runs on each GPFS (DSS-G) server
to create the snapshot only if the node is currently the cluster master, as in:
*/15 * * * * root mmlsmgr -Y | grep -q "clusterManager.*:$(hostname
--long):" && /path/to/snapshotter
This requires no locking and ensures that only a single instance of snapshots
is created at each time interval.
We use the same trick to gather GPFS health stats, etc., ensuring that the data
collection only runs on a single node (the cluster manager).
--
Mark Bergman voice: 215-746-4061
mark.berg...@pennmedicine.upenn.edu fax: 215-614-0266
http://www.med.upenn.edu/cbica/
IT Technical Director, Center for Biomedical Image Computing and Analytics
Department of Radiology University of Pennsylvania
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