On 5/31/2011 10:22 AM, Roskens, Ronald wrote:
> Yes. I've been running with store-by-group for over a year now. Not sure if
> its helping or not. Will assume that it is.
>
> The main flaw that I see with JRobin& store-by-group is that's a compounded
> problem. Its not something you see when you look at it up close, you need to
> step back and look at it from whats happening at the OS level. The JRobin
> file format spreads its definition format all throughout the file. Each time
> you open the file, JRobin has to scan through it all so it "knows" where to
> read/write any updates. If you're application is continually opening and
> closing the files then you'll be ok as long as the total jrobin dataset is
> able to be cached by the OS's file buffercache. If you got beyond that limit,
> then the OS will have to continually read the blocks of the JRobin files into
> memory upon each open().
>
> So with a large enough number of nodes+data collection points, OpenNMS+JRobin
> degenerates down to a pure random read/writes at the block level of your
> storage system leaving us with the worst case performance scenario.
>
> My system has no problems doing the actual polling& datacollection. Its just
> that OpenNMS+JRobin causes it to not be able to write the data collected out
> to disk without having a large operations pending. Hence, whenever I
> restarted OpenNMS, my graphs all end up with a 30-60 minute block of no data
> to display.
But if you use application memory for the cache, you'll have that much
less in the OS cache. Why not give up and add RAM to the server?
--
Les Mikesell
lesmikes...@gmail.com
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