Quick DataStax OpsCenter question

[Alexandru Dan Sicoe <si...@googlemail.com>]

Hi,

 I'm using the community version of OpsCenter to monitor my clutster. At
the moment I'm interested in storage space. In the performance metrics
page, if I choose to see the graph of a the metric "CF: SSTable Size" for a
certain CF of interest,  two things are plotted on the graph: Total disk
used (Total) and Live disk used (Total). Does anyone know what they mean?
And what is the difference? "Total disk used" gives me the same value as
the size on disk of the files corresponding to the CF in the data directory
(all files starting with CF name and having Statistics, Data, Filter, Index
or Compacted). But what is the "Live disk used"? I thought it is just the
raw data on disk (column names and values) without any SSTable overhead,
but this is not true because it reports a lower value than if I see the
disk usage of just the "CFName-..-Data.db" files.
 I'm always confused about what all the metrics in the OpsCenter mean and
how they are calculated. Is there a reference explaining all of them? Most
are mapped to the JMX attributes exposed...but even for those, I've never
found a reference explaining them in detail. Any suggestions?

Cheers,
Alexandru

P.S.  I'm using Cassandra 0.8.5

Re: Quick DataStax OpsCenter question

[Nick Bailey <ni...@datastax.com>]

Live Disk Space indicates all sstables that are currently valid. Total
Disk Space will include sstables that have been compacted but not yet
deleted (because a full GC hasn't run yet).

Also the 1.3 release of OpsCenter includes an inline help section. You
can find more specific information about performance metrics under the
Performance section of the help.

On Thu, Nov 17, 2011 at 7:35 AM, Alexandru Dan Sicoe
<si...@googlemail.com> wrote:
> Hi,
>
>  I'm using the community version of OpsCenter to monitor my clutster. At the
> moment I'm interested in storage space. In the performance metrics page, if
> I choose to see the graph of a the metric "CF: SSTable Size" for a certain
> CF of interest,  two things are plotted on the graph: Total disk used
> (Total) and Live disk used (Total). Does anyone know what they mean? And
> what is the difference? "Total disk used" gives me the same value as the
> size on disk of the files corresponding to the CF in the data directory (all
> files starting with CF name and having Statistics, Data, Filter, Index or
> Compacted). But what is the "Live disk used"? I thought it is just the raw
> data on disk (column names and values) without any SSTable overhead, but
> this is not true because it reports a lower value than if I see the disk
> usage of just the "CFName-..-Data.db" files.
>  I'm always confused about what all the metrics in the OpsCenter mean and
> how they are calculated. Is there a reference explaining all of them? Most
> are mapped to the JMX attributes exposed...but even for those, I've never
> found a reference explaining them in detail. Any suggestions?
>
> Cheers,
> Alexandru
>
> P.S.  I'm using Cassandra 0.8.5