Tombstone_failure_threshold is only for reads. If the tombstones are in different partitions, and you aren’t doing cross-partition reads, you shouldn’t need to adjust that value.
If disk space recovery is the goal, it depends on how available you need the data to be. The faster way is probably to unload the 2 billion you want to keep, truncate the table, reload the 2 billion. But you might have some data unavailable during the reload. Can the app tolerate that? Dsbulk can make this much faster than previous methods. The tombstone + compaction method will take a while, and could get tricky if some nodes are close to the limit for compaction to actually occur. You would want to adjust gc_grace to a low (but acceptable) time and probably turn on unchecked_tombstone_compaction with a low tombstone threshold (0.1 or lower?). You would probably still need to force a major compaction to get rid of data where the tombstones are in different sstables than the original data (assuming size-tiered). This is all much more tedious, error-prone, and requires some attention to each node. If a node can’t compact, you might have to wipe it and rebuild/re-add it to the cluster. Sean Durity From: Pushpendra Rajpoot <pushpendra.nh.rajp...@gmail.com> Sent: Friday, November 20, 2020 10:34 AM To: user@cassandra.apache.org Subject: [EXTERNAL] how to choose tombstone_failure_threshold value if I want to delete billions of entries? Hi Team, I have a table having approx 15 billions entries and I want to delete approx 13 billions entries from it. I cannot write 13 billion tombstones in one go since there is a disk space crunch. I am planning to delete data in chunks so I will be creating 400 millions tombstones in one go. Now, I have 2 questions: 1. What is the optimal value of the tombstone_failure_threshold for the above scenario? 2. What is the best way to delete 13 billions entries in my case ? Regards, Pushpendra ________________________________ The information in this Internet Email is confidential and may be legally privileged. It is intended solely for the addressee. Access to this Email by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or any action taken or omitted to be taken in reliance on it, is prohibited and may be unlawful. When addressed to our clients any opinions or advice contained in this Email are subject to the terms and conditions expressed in any applicable governing The Home Depot terms of business or client engagement letter. The Home Depot disclaims all responsibility and liability for the accuracy and content of this attachment and for any damages or losses arising from any inaccuracies, errors, viruses, e.g., worms, trojan horses, etc., or other items of a destructive nature, which may be contained in this attachment and shall not be liable for direct, indirect, consequential or special damages in connection with this e-mail message or its attachment.
