Cassandra: how to automatically delete old records to avoid disk space shortage?

Question

We are using TWCS for time series data with default TTL of 30 days an compaction window size of 1 day.

Unfortunately, there are cases when incoming data rate gets higher and not so much disk space left to write it. At the same time due to budget constraints adding new nodes to the cluster is not an option. Currently we resort to manually deleting old sstables, but it is error prone.

What is the best way in TWCS case to make Cassandra delete, say, all records that are older than certain date? I mean not to create tombstones in new sstable, but to actually delete old records from disk to free up space.

Of course, I can reduce TTL, but it will affect only new records (so will help only in a long run, but not immediately) and in a case when there is not so much incoming data records will be stored for a shorter period than could be.

Answer 1

Basically, that's the intent of the TTLs to automatically remove the old data. The explicit deletion always creates a tombstone, and it won't work well with with TWCS. So right now the solution would be to stop node, remove old files to free space, start the node - repeat on all nodes. But you're doing that already.