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From <>
Subject RE: Removal of old data files
Date Thu, 01 Sep 2011 22:11:22 GMT
Yes, I see files with name like

However, all of those file have a size of 0.

Starting from Monday to Thurseday we have 5642 files for -Data.db, -Filter.db and Statistics.db
and only 128 -Compacted files.
and all of -Compacted file has size of 0.

Is this normal, or we are doing something wrong?


From: aaron morton []
Sent: Thursday, August 25, 2011 6:13 PM
Subject: Re: Removal of old data files

If cassandra does not have enough disk space to create a new file it will provoke a JVM GC
which should result in compacted SStables that are no longer needed been deleted. Otherwise
they are deleted at some time in the future.

Compacted SSTables have a file written out with a "compacted" extension.

Do you see compacted sstables in the data directory?


Aaron Morton
Freelance Cassandra Developer

On 26/08/2011, at 2:29 AM, yuki watanabe wrote:

We are using Cassandra 0.8.0 with 8 node ring and only one CF.
Every column has TTL of 86400 (24 hours). we also set 'GC grace second' to 43200
(12 hours).  We have to store massive amount of data for one day now and eventually for five
days if we get more disk space.
Even for one day, we do run out disk space in a busy day.

We run nodetool compact command at night or as necessary then we run GC from jconsole. We
observed that  GC did remove files but not necessarily oldest ones.
Data files from more than 36 hours ago and quite often three days ago are still there.

Does this behavior expected or we need adjust some other parameters?

Yuki Watanabe


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