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From Anand Somani <meatfor...@gmail.com>
Subject Re: what's the difference between repair CF separately and repair the entire node?
Date Wed, 14 Sep 2011 18:05:48 GMT
On Tue, Sep 13, 2011 at 3:57 PM, Peter Schuller <peter.schuller@infidyne.com
> wrote:

> > I think it is a serious problem since I can not "repair".....  I am
> > using cassandra on production servers. is there some way to fix it
> > without upgrade?  I heard of that 0.8.x is still not quite ready in
> > production environment.
>
> It is a serious issue if you really need to repair one CF at the time.
>
Why is it serious to do repair one CF at a time, if I cannot do that it at a
CF level, then does it mean that I cannot use more than 50% disk space? Is
this specific to this problem or is that a general statement? I ask because
I am planning on doing this so I can limit the max disk overhead to be a CF
(+ some factor) worth. I am going to be testing this in the next couple of
weeks or so.

> However, looking at your original post it seems this is not
> necessarily your issue. Do you need to, or was your concern rather the
> overall time repair took?
>
> There are other things that are improved in 0.8 that affect 0.7. In
> particular, (1) in 0.7 compaction, including validating compactions
> that are part of repair, is non-concurrent so if your repair starts
> while there is a long-running compaction going it will have to wait,
> and (2) semi-related is that the merkle tree calculation that is part
> of repair/anti-entropy may happen "out of synch" if one of the nodes
> participating happen to be busy with compaction. This in turns causes
> additional data to be sent as part of repair.
>
> That might be why your immediately following repair took a long time,
> but it's difficult to tell.
>
> If you're having issues with repair and large data sets, I would
> generally say that upgrading to 0.8 is recommended. However, if you're
> on 0.7.4, beware of
> https://issues.apache.org/jira/browse/CASSANDRA-3166
>
> --
> / Peter Schuller (@scode on twitter)
>

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