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From Dominic Williams <dwilli...@fightmymonster.com>
Subject Re: deleting rows and tombstones
Date Tue, 14 Feb 2012 22:30:36 GMT
Hi that's a good question. Maybe we are hanging on to lessons we shouldn't
need but...

Currently even on 1.07 we still get significant deleted data popping when
repair hasn't run.

The irony is that it is usually cluster disruption caused by
repair-initiated compaction storms that seem to be the driver of these
problems(!) but what that shows is that ideally you still need to run
repair processes

Incidentally, the primary purpose of CASSANDRA-3620 is not to prevent data
popping up when repair hasn't been run, but rather to improve performance
by allowing tombstones to be removed by compaction at the earliest
opportunity (or even to be removed before they even make it into an
sstable). As they build up they can affect performance badly. I'd like to
see the end of the whole idea of GCGradeSeconds.

On 14 February 2012 21:29, Todd Burruss <bburruss@expedia.com> wrote:

> do you find that repair is still as necessary now since hinted handoffs
> are stored anytime a node does not ACK successfully?
>
>  From: Dominic Williams <dwilliams@fightmymonster.com>
> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org>
> Date: Tue, 14 Feb 2012 12:31:45 -0800
>
> To: "user@cassandra.apache.org" <user@cassandra.apache.org>
> Subject: Re: deleting rows and tombstones
>
> Hi Todd,
>
> Our systems do a lot of deletions and it does cause problems.
>
> Your best bet is to bring GCSeconds low and run repair religiously. The
> issue you can run into though is repair overloading your servers when your
> data load gets high, repair falling over and related problems.
>
> IMHO the need to run repair really needs to be addressed urgently.
>
> I proposed an alternative approach here
> https://issues.apache.org/jira/browse/CASSANDRA-3620 so vote it up if you
> share problems!
>
> Dominic
>
> On 14 February 2012 19:54, Todd Burruss <bburruss@expedia.com> wrote:
>
>> my design calls for deleting a row (by key, not individual columns) and
>> re-inserting it a lot and I'm concerned about tombstone build up slowing
>> down reads.  I know if I delete a lot of individual columns the tombstones
>> will build up and slow down reads until they are cleaned up, but not sure
>> if the same holds for deleting the whole role.
>>
>> thoughts?
>>
>
>

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