Disk space not changed after massive data removal from Cassandra db with compaction and repair

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Disk space not changed after massive data removal from Cassandra db with compaction and repair

We have a Cassandra cluster (2.1.11) with 15 nodes, replication factor 3 on SSD drives.
One of the table occupies 12 TB. Both live disk space and total disk space are equivalent. I also verified this number is the same on Ops center, JMX reports, and actual folder size on the file system.
We’re getting in short of space, so we have removed 35% of the entire data. (each entry has 104 bytes, so we removed billions of rows)
However, we have gained no free space at all, although we see a lot of compactions going on while we delete entries.
Since then, we ran nodetool repair / nodetool clean / restart process jvm, no luck.
Does anybody know any other thing I can do?

Solutions/Answers:

Solution 1:

Assume you’ll have to wait gc_grace_seconds before the deleted data are eligible for getting their generated tombstones finally removed. So plan ahead in due time 🙂

Here’s a good link on understanding the inner working of Cassandra and delete vs release of disk space. And maybe consider this link as well on howto do user defined compaction.

References

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