Hi,
I am starting to work on a ganglia to PCP archive converter as
highlighted here:
http://oss.sgi.com/bugzilla/show_bug.cgi?id=1078
Since rrd and pcp both have a perl api, the conversion is pretty
straightforward. The one issue might be that the rrd files are already
rate converted or averaged or whatever you want to call it. So for what
PCP would consider counter metrics (network packets, bytes transferred,
etc) ganglia gives you only the change between sampling intervals, not
the raw counter value. This is not a problem when constructing an
archive from existing ganglia files at a single point in time since you
can accumulate the counter values, but might be an issue when you want
to, for instance, convert ganglia archives to pcp format as a daily cron
job for the previous 24 hour period.
In this case, if you constructed a pcp archive each day
containingin the previous 24 hours ganglia data, if you didn't do some
sort of state saving, each metric would start off at a raw counter value
of zero. Then at some later time, if you wanted to pmlogextract for a
time period that spanned multiple of these converted logs, you would get
a discontinuity when these "counters" reset to zero.
Or does all this just get handled properly by client tools when
they see the "MARK" records that pmlogextract would put in these locations?
I haven't gotten far enough along to actually test what happens,
was just wondering what I should expect.
Thanks
Martins
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