Why without -PR when recovering from crash?

Repair without -PR runs full repair of the cluster, the node which receives a 
command is a repair controller, ALL nodes synchronizes replicas at the same 
time, streaming data between each other.
The problems may arise:

·         When streaming hangs (it tends to hang even on a stable network), 
repair session hangs (any version does re-stream?)

·         Network will be highly saturated

·         In case of high inconsistency some nodes may receive a lot of data, 
disk usage much more than 2x (depends on RF)

·         A lot of compactions will be pending

IMO, best way to run repair is from script with -PR for single CF from single 
node at a time and monitoring progress, like:
repair -pr node1 ks1 cf1
repair -pr node2 ks1 cf1
repair -pr node3 ks1 cf1
repair -pr node1 ks1 cf2
repair -pr node2 ks1 cf2
repair -pr node3 ks1 cf2
With some progress or other control in between, your choice.

Use repair with care, do not let your cluster go down.





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Senior Developer

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From: R. Verlangen [mailto:ro...@us2.nl]
Sent: Monday, June 04, 2012 15:17
To: user@cassandra.apache.org
Subject: Re: repair

The "repair -pr" only repairs the nodes primary range: so is only usefull in 
day to day use. When you're recovering from a crash use it without -pr.
2012/6/4 Romain HARDOUIN 
<romain.hardo...@urssaf.fr<mailto:romain.hardo...@urssaf.fr>>

Run "repair -pr" in your cron.

Tamar Fraenkel <ta...@tok-media.com<mailto:ta...@tok-media.com>> a écrit sur 
04/06/2012 13:44:32 :

> Thanks.
>
> I actually did just that with cron jobs running on different hours.
>
> I asked the question because I saw that when one of the logs was
> running the repair, all nodes logged some repair related entries in
> /var/log/cassandra/system.log
>
> Thanks again,
> Tamar Fraenkel
> Senior Software Engineer, TOK Media



--
With kind regards,

Robin Verlangen
Software engineer

W www.robinverlangen.nl<http://www.robinverlangen.nl>
E ro...@us2.nl<mailto:ro...@us2.nl>

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