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From Paolo Crosato <>
Subject CF performance suddenly degraded
Date Mon, 22 Dec 2014 16:58:15 GMT

I declared this CF:

CREATE TABLE timesliceunitstate (
   day timestamp,
   unitbuckets text,
   PRIMARY KEY (day)

unitbuckets is a text column holding a fairly big amount of data, around 
30 MB of json text per row.

The table is holding 30 rows, I'm running cassandra 2.0.8 on a 3 nodes 
cluster with replication factor of 3, consistency of reads is quorum, so 
2 out of 3 nodes.

The table has a write hit about every 20 minutes, which updates only one 
row, the most recent.

I had no problem with read queries (I query the table one row at time) 
until this morning, when read latency jumped from around 300ms to 20 
seconds for each query.

I tried repairing the table on all the 3 nodes using range repair 
without success, the *Data.db file on the disk is aorund 30 MB, so a bit 
less than 1MB for each row.

I'm using latest version of datastax driver, 2.1. I changed nothing on 
the application level since days, so it's not something related to the 
applicacation or the driver.

Is there anyway I can troubleshoot the issue and discover what's making 
the table so slow?

Thanks for any advice,


Paolo Crosato
Software engineer/Custom Solutions

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