Take a basic mminfo query, add someone not familiar with how NetWorker stores and works with dates\/times, and you have instant chaos*. In this post I want to help people who are just starting out with mminfo understand how it works with dates.<\/p>\n
So let’s look at a basic query that tends to cause a lot of confusion:<\/p>\n
# mminfo -q \"client=archon,savetime<=2 weeks ago\"<\/pre>\nAs a long-term NetWorker user, and implementation consultant\/support consultant, not to mention a long term member of the NetWorker mailing list, this question seems to come up fairly frequently. The output appears “broken” – rather than being “savetime less than or equal to two weeks ago”, we instead get all backups for the client archon where the savetime is greater than or equal to<\/em> two weeks ago.<\/p>\n
‘Huh?’<\/em> I hear you ask.<\/p>\n
Indeed, this is oft-used as an example of how “broken” NetWorker is. In fact, the real state is far more prosaic.<\/p>\n
NetWorker stores and works with times as seconds since the(\/an) epoch. When you supply dates to NetWorker – either in the fuzzy format above, or as a literal date string, it converts that date into a timestamp of seconds since the(\/an) epoch. (You can if you want find out what a savetime is in seconds, rather than an interpreted date any time you wish in mminfo by choosing a report specification of ‘nsavetime’.)<\/p>\n
So if you then think of the query:<\/p>\n
# mminfo -q \"client=archon,savetime<=2 weeks ago\"<\/pre>\nIt has a different meaning. You’re actually asking NetWorker:<\/p>\n
\n
- Convert ‘2 weeks ago’ into seconds offset from ‘now’. Let’s call that Z<\/em>.<\/li>\n
- Give me all the backups for the client ‘archon’ where the savetime is less than or equal to Z<\/em>.<\/li>\n<\/ul>\n
If you don’t like to think of it as all referring to seconds since an epoch, there’s another, perhaps simpler way of thinking about it – that being:<\/p>\n
\n
- Treat “<” as meaning before<\/strong><\/em>.<\/li>\n
- Treat “>” as meaning after<\/strong><\/em>.<\/li>\n<\/ul>\n
Thus, in this scenario, the query:<\/p>\n
# mminfo -q \"client=archon,savetime<=2 weeks ago\"<\/pre>\nCan be interpreted to mean, “give me all backups of the client archon taken before<\/em> two weeks ago”.<\/p>\n
You’re obviously welcome to use whichever interpretation you feel makes more sense – seconds\/math or before\/after – it doesn’t really matter which. Once you get the hang of this though mminfo will make a lot more sense.<\/p>\n
—<\/p>\n
* I’ve unfortunately seen someone who got < and > wrong (and didn’t check their results) relabel all tapes in a tape library that had backups younger than 3 months, rather than older than 3 months. Hence, ‘chaos’ is an appropriate term.<\/p>\n","protected":false},"excerpt":{"rendered":"
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