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Re: Discovery, pmfind, pmmgr - initial review notes

To: Nathan Scott <nathans@xxxxxxxxxx>
Subject: Re: Discovery, pmfind, pmmgr - initial review notes
From: "Frank Ch. Eigler" <fche@xxxxxxxxxx>
Date: Mon, 6 Jan 2014 06:48:43 -0500
Cc: Ken McDonell <kenj@xxxxxxxxxxxxxxxx>, PCP Mailing List <pcp@xxxxxxxxxxx>
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Hi, Nathan -

> > The current code does a log-merge of all previous archives into one,
> > doing data-aging at the same time, so thar particular type of trash
> > doesn't pile up.
> 
> /me re-reads the code ... I'm not following what you mean by "doing
> data-aging"?  

I was referring to using the "-S NNN" parameter for the pmlogextract
merging, ie., simply dropping data beyond a certain age.


> There is a pmlogreduce(1) tool - but its not used by pmmgr AFAICS.

Yes, I'd like to use that sort of gradual downsampling/aging at some
point as an optional alternative to simply dropping old data.


> Anyway, some people will not want to data reduce and will want to keep
> their original high precision data [...] (I'm assuming a
> single archive for high precision data over months/years is not really
> feasible with the current archive format - but maybe thats something
> we could tackle instead).  

I'd love to tackle that instead, definitely, if it doesn't Just Work
already.  At some point, when we have a log-archive server, it will be
desirable to have as few input archive files to monitor as possible.


> [...]  If we're attempting log merging to the level I later realised
> you may be doing (one archive to rule them all), [pmlogrewrite]
> quickly becomes a pressing need as merging is impossible without it
> (when PMDA evolution occurs, as described in pmlogrewrite(1) para
> #2).

Got it.


- FChE

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