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<== Date ==> <== Thread ==>

Subject: Re: RDB archiver disk space
From: "Konrad, Martin" <konrad@frib.msu.edu>
To: Jiro Fujita <jiro.fujita@gmail.com>
Cc: EPICS tech-talk <tech-talk@aps.anl.gov>
Date: Fri, 19 Jul 2013 14:43:14 +0000
Hi,
> One of the question being asked that I have no information is that how
> much disk space would it really needs?
That pretty much depends on what you are archiving: What kind of PV
(datatype)? What's the update rate (keep in mind that monitoring
death-bands can make it difficult to predict the average rate)? Adding
an index to your database to speed up data retrieval can roughly double
the amount of disk space you need. With MySQL you can use different
storage engines which will give you different storage efficiency.

So long story short: The easiest thing is to give it a try. Set
everything up on a PC or virtual machine and measure yourself. According
to my experience you do not need a high performance machine for a test.
If your disk is too slow, switch off regular flushing to disk. But keep
in mind that you can lose your data with a setup like this. See [1] for
some details you might want to consider for a production machine (most
of it should apply to MySQL as well).

If you're striving for high storage efficiency, you might even want to
look at transparent filesystem compression like it is included in ZFS.

Best regards,

Martin

[1] http://accelconf.web.cern.ch/AccelConf/pcapac2012/papers/wepd03.pdf


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Re: RDB archiver disk space Jiro Fujita

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