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From Ben Kaehne <ben.kae...@sirca.org.au>
Subject Cassandra startup times
Date Thu, 19 Jul 2012 04:54:14 GMT
Good evening,

I am interested in improving the startup time of our cassandra cluster.

We have a 3 node cluster (replication factor of 3) in which our application
requires quorum reads and writes to function.

Each machine is well specced with 24gig of ram, 10 cores, jna enabled etc.

On each server our keyspace files are so far around 90 Gb (stored on NFS
although I am not seeing signs that we have much network io). This size
will grow in future.

Our startup time for 1 server at the moment is greater then half an hour
(45 minutes to 50 minutes even) which is putting a risk factor on the
resiliance of our service. I have tried version 1.09 to latest 1.12.

I do not see too much system utilization while starting either.

I gazed apon an article suggesting increased speed in 1.2 although when I
set it up, it did not seem to be any faster at all (if not slower).

I was observing what was happening during startup and I noticed (via
strace), cassandra was doing lots of 8 byte reads from:

 /var/lib/cassandra/data/XXXXXX/YYYYYY/XXXXXXX-YYYYYYY-hc-1871-CompressionInfo.db
 /var/lib/cassandra/data/XXXXXX/YYYYYY/XXXXXXX-YYYYYYY-hc-1874-CompressionInfo.db

Also... Is there someone I can change the 8 byte reads to something
greater? 8 byte reads across NFS is terribly inefficient (and I am guessing
the cause of our terribly slow startup times).

Regards,

-- 
-Ben

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