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From Marcus Eriksson <krum...@gmail.com>
Subject Re: Transitioning to incremental repair
Date Tue, 01 Dec 2015 14:34:22 GMT
Yes, it should now be safe to just run a repair with -inc -par to migrate
to incremental repairs

BUT, if you currently use for example repair service in OpsCenter or
Spotifys Cassandra reaper, you might still want to migrate the way it is
documented as you will have to run a full repair to migrate to incremental
repairs, not many sub range repairs and that might not be possible for some
users with a lot of data or with vnodes etc.

I would also wait until
https://issues.apache.org/jira/browse/CASSANDRA-10768 has been committed
and released as it will improve anticompaction performance

/Marcus

On Tue, Dec 1, 2015 at 3:24 PM, Sam Klock <sklock@akamai.com> wrote:

> Hi folks,
>
> A question like this was recently asked, but I don't think anyone ever
> supplied an unambiguous answer.  We have a set of clusters currently
> using sequential repair, and we'd like to transition them to
> incremental repair.  According to the documentation, this is a very
> manual (and likely time-consuming) process:
>
>
> http://docs.datastax.com/en/cassandra/2.1/cassandra/operations/opsRepairNodesMigration.html
>
> Our understanding is that this process is necessary for tables that use
> LCS, as unrepaired tables are compacted using STCS and (without the
> process described in the doc) all tables start in the unrepaired
> state.  The pain of this migration strategy is supposed to be offset by
> the savings in undesired compaction activity.  The docs aren't
> especially clear, but it sounds like this strategy is not needed for
> tables that use STCS.
>
> However, CASSANDRA-8004 (resolved against 2.1.2) appears intended to
> have both the repaired and unrepaired sstable sets use the same
> compaction strategy.  It seems like that obviates the rationale for a
> migration procedure, which is supported by offhand comments on this
> list, e.g.:
>
> https://www.mail-archive.com/user%40cassandra.apache.org/msg40303.html
> https://www.mail-archive.com/user%40cassandra.apache.org/msg44896.html
>
> In other words, it *looks* like the docs are obsolete, and the
> migration process for existing clusters only consists of flipping the
> switch (i.e., adding "-inc" to invocations of "nodetool repair").
>
> Our questions:
>
> 1) Is our understanding of the status quo following 2.1.2 correct?
> Does migrating existing clusters to incremental repair only require
> adding the "-inc" argument, or is a process still required?
>
> 2) If a process is still required, have there been any changes since
> 2.1.2?  Are the docs up-to-date?
>
> 3) If there is no process or if the process has changed, are there
> plans on the DataStax side to update the documentation accordingly?
>
> Thanks,
> SK
>

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