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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: TotalDiskSpaceUsed and LiveDiskSpaceUsed
Date Mon, 24 Oct 2011 16:44:09 GMT
On Mon, Oct 24, 2011 at 6:26 PM, Rene Kochen
<Rene.Kochen@emea.schange.com> wrote:
> What is the difference between these JMX column family attributes:
>
>
>
> TotalDiskSpaceUsed  and LiveDiskSpaceUsed

Prior to Cassandra 1.0, obsolete data files (compacted ones) were not
deleted right away,
but potentially quite some times after they become obsolete. In that
setting, TotalDiskSpaceUsed
represents the total of the space used by sstables (live *and*
obsolete waiting to be deleted)
while LiveDiskSpaceUsed was only the live ones.

In 1.0, obsolete data files are deleted as soon as they are not needed
anymore, so those
two attributes should be essentially the same, we just haven't merged
them yet (though there
is a few situations (with mmap on non-sun jvm) where data file may
still take some time to be
deleted, so we may keep the two settings for some times).

--
Sylvain

>
>
>
> Thanks!
>
>
>
> Rene

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