CODEWITHSUNDEEP
cassandra
Rubycut
Rubycut

Reputation: 1646

Cassandra 2.0 eating disk space

I am using cassandra in my app and it started eating up disk space much faster than I expected and much faster than defined in manual. Consider this most simple example:

CREATE TABLE sizer (
    id ascii,
    time timestamp,
    value float,
    PRIMARY KEY (id,time)
  ) WITH compression={'sstable_compression': ''}"

I am turning off compression on purpose to see how many bytes will each record take.

Then I insert few values, I run nodetool flush and then I check the size of data file on disk to see how much space did it take.

Results show huge waste of space. Each record take 67 bytes, I am not sure how that is possible.

My id is 13 bytes long at it is saved only once in data file, since it is always the same for testing purposes.

According to: http://www.datastax.com/documentation/cassandra/2.0/webhelp/index.html#cassandra/architecture/architecturePlanningUserData_t.html

Size should be:

For testing sake, my id is always same, so I have actually only 1 row if I understood correctly.

So, my questions is how do I end up on using 67 bytes instead of 33.

Datafile size is correct, I tried inserting 100, 1000 and 10000 records. Size is always 67 bytes.

Upvotes: 0

Views: 449

Answers (1)

Peter Halliday
Peter Halliday

Reputation: 301

There are 3 overheads discussed in the file. One is the column overhead, which you have accommodated for. The second is the row overhead. And also if you have replication_factor greater than 1 there's an over head for that as well.

Upvotes: 2

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