TTL is good for this but I have no idea how you will ever be able to restore data removed from disk like that. Perhaps one could make a snapshot and then delete everything with timestamp older than a date and then run compaction on every node to reclaim the disk.
2014-04-28 21:57 GMT+02:00 Donald Smith <donald.sm...@audiencescience.com>: > CQL lets you specify a default TTL per column family/table: and > default_time_to_live=86400 . > > > > *From:* Redmumba [mailto:redmu...@gmail.com] > *Sent:* Monday, April 28, 2014 12:51 PM > *To:* user@cassandra.apache.org > *Subject:* Re: Cassandra data retention policy > > > > Have you looked into using a TTL? You can set this per insert > (unfortunately, it can't be set per CF) and values will be tombstoned after > that amount of time. I.e., > > INSERT INTO .... VALUES ... TTL 15552000 > > Keep in mind, after the values have expired, they will essentially become > tombstones--so you will still need to run clean-ups (probably daily) to > clear up space. > > Does this help? > > One caveat is that this is difficult to apply to existing rows--i.e., you > can't bulk-update a bunch of rows with this data. As such, another good > suggestion is to simply have a secondary index on a date field of some > kind, and run a bulk remove (and subsequent clean-up) daily/weekly/whatever. > > > > On Mon, Apr 28, 2014 at 11:31 AM, Han Jia <johnideal...@gmail.com> wrote: > > Hi guys, > > > > > > We have a processing system that just uses the data for the past six > months in Cassandra. Any suggestions on the best way to manage the old data > in order to save disk space? We want to keep it as backup but it will not > be used unless we need to do recovery. Thanks in advance! > > > > > > -John > > >
