Hi,
Compaction can block reads, but on the write path you should be able to absorb a certain amount of writes via the WAL before rocksdb starts throttling writes. The larger and more WAL buffers you have, the more writes you can absorb, but bigger buffers also take more CPU to keep in sorted order and more aggregate buffer uses more RAM so it's a double edged sword. I'd suggest looking and seeing how much time you actually spend in compaction. For clusters that primarily are serving block via RBD, there's a good chance it's actually fairly minimal. For RGW (especially with lots of small objects and/or using erasure coding) you might be spending more time in compaction, but it's important to see how much.
FWIW, you can try running the following script against your OSD log to see a summary of compaction events:
https://github.com/ceph/cbt/blob/master/tools/ceph_rocksdb_log_parser.py Mark On 11/15/21 10:48 AM, Szabo, Istvan (Agoda) wrote:
Hello, If I’m not mistaken in my cluster this can block io on the osds if have a huge amount of objects on that specific osd. How can I change the values to minimise the impact? I guess it needs osd restart to make it effective and the “rocksdb options” are the values that needs to be tuned, but what should it be changed? Istvan Szabo Senior Infrastructure Engineer --------------------------------------------------- Agoda Services Co., Ltd. e: istvan.sz...@agoda.com<mailto:istvan.sz...@agoda.com> --------------------------------------------------- _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-le...@ceph.io
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