[ceph-users] What goes in the monitor database?

Bryan Henderson bryanh at giraffe-data.com
Sat Nov 4 13:35:41 PDT 2017


Hi.  Can anyone give me a rough idea of what the monitor database is for?  I'm
curious about how it is behaving in an experimental system I set up.

I have a single monitor and a single client that just connects once a second
and does a "status" command.  There is one OSD and one MDS in there too.  This
is a Hammer system with a LevelDB key-value store.  This produces a fair
amount of activity in the database; it looks like about 25K of updates for
every "status" transaction.  The database compacts periodically and over the
longrun, does not grow in size.

Using ceph_kvstore_tool after shutting down the monitor, I see hundreds of
keys.

So what does the monitor have to store to do a "status" command?

I've seen clues that the activity has to do with Paxos elections, but I'm
fuzzy on why elections would be happening or why they would need a persistent
database.

-- 
Bryan Henderson                                   San Jose, California


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