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[chrismd <question79783@xxxxxxxxxxxxxxxxxxxxx>]

Question #79783 on Graphite changed:
https://answers.launchpad.net/graphite/+question/79783

    Status: Open => Answered

chrismd proposed the following answer:
Yes, if your retentions line looked like so:

retentions = 900:4,3600:24,86400:7,604800:4

Then the precision of data returned for a particular request (a graph or
raw data) will depend on the time range you are requesting. Anything
within the past hour will be returned at 15 minute precision, within the
past day at hourly precision, within the past week at daily precision,
and within the past 4 weeks at weekly precision. Whisper returns data at
the finest precision possible for the time range you give it.

One thing I feel I should mention though is that the idea behind having
multiple archives at varying levels of precision is intended to save
space when you have a lot of data with long-term retention requirements.
With this configuration your database files will be very very small (532
bytes to be exact), so my recommendation would be to actually store the
whole 30 days at a higher precision like 15 minutes (which would make
the files 35 kilobytes each). Otherwise, viewing the whole past month
will give you a graph with at most 4 data points in it, one for each
week.

If your goal is to have graphs that show a particular precision though
what you could do right now (since I do not have anything implemented to
allow you to request a specific precision in your output) is simply
store the data in multiple archives each with a different level of
precision configured. For example, com.cnn.popularity.foo.15min and
com.cnn.popularity.1hour, etc... That way you could view all your data
at 15-minute precision, hourly precision, daily, weekly, whatever. This
would of course be wasteful in terms of disk space, the better solution
would be to implement a graphing option to aggregate data points at
render time.

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