** Description changed:
- For a certain type of workload, the bluefs might never compact the log file,
- which would cause the bluefs log file slowly grows to a huge size
+ [Impact]
+
+ For a certain type of workload, the bluefs might never compact the log
+ file, which would cause the bluefs log file slowly grows to a huge size
(some bigger than 1TB for a 1.5T device).
- This bug could eventually cause osd crash and failed to restart as it
couldn't get through the bluefs replay phase during boot time.
- We might see below log when trying to restart the osd:
- bluefs mount failed to replay log: (5) Input/output error
-
There are more details in the bluefs perf counters when this issue happened:
- e.g.
+ e.g.
"bluefs": {
"gift_bytes": 811748818944,
"reclaim_bytes": 0,
"db_total_bytes": 888564350976,
"db_used_bytes": 867311747072,
"wal_total_bytes": 0,
"wal_used_bytes": 0,
"slow_total_bytes": 0,
"slow_used_bytes": 0,
"num_files": 11,
"log_bytes": 866545131520,
"log_compactions": 0,
"logged_bytes": 866542977024,
"files_written_wal": 2,
"files_written_sst": 3,
"bytes_written_wal": 32424281934,
"bytes_written_sst": 25382201
}
- As we can see the log_compactions is 0, which means it's never compacted and
the log file size(log_bytes) is already 800+G. After the compaction, the log
file size would reduced to around
- 1 G
+ This bug could eventually cause osd crash and failed to restart as it
couldn't get through the bluefs replay phase during boot time.
+ We might see below log when trying to restart the osd:
+ bluefs mount failed to replay log: (5) Input/output error
- Here is the PR[1] that addressed this bug, we need to backport this to ubuntu
12.2.13
- [1] https://github.com/ceph/ceph/pull/17354
+ As we can see the log_compactions is 0, which means it's never compacted
+ and the log file size(log_bytes) is already 800+G. After the compaction,
+ the log file size would need to be reduced to around 1G.
+
+ [Test Case]
+
+ Deploy a test ceph cluster (Luminous 12.2.13 which has the bug) and
+ drive I/O. The compaction doesn't get triggered often when most I/O are
+ reads. So fill up the cluster initially with lots of writes and then
+ start reading heavy reads (no writes). Then the problem should occur.
+ Smaller sized OSDs are OK as we'are only interested filling up the OSD
+ and grow the bluefs log.
+
+ [Where problems could occur]
+
+ This fix has been part of all upstream releases since Mimic, so there's been
quite good "runtime".
+ The changes ensure that compaction happens more often. But that's not going
to cause any problem.
+ I can't see any real problems.
+
+ [Other Info]
+ - It's only needed for Luminous (Bionic). All new releases since have this
already.
+ - Upstream PR: https://github.com/ceph/ceph/pull/17354
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https://bugs.launchpad.net/bugs/1914911
Title:
[SRU] bluefs doesn't compact log file
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