On 12 Jan 2015, at 17:08, Sage Weil <s...@newdream.net<mailto:s...@newdream.net>> wrote:
On Mon, 12 Jan 2015, Dan Van Der Ster wrote: Moving forward, I think it would be good for Ceph to a least document this behaviour, but better would be to also detect when zone_reclaim_mode != 0 and warn the admin (like MongoDB does). This line from the commit which disables it in the kernel is pretty wise, IMHO: "On current machines and workloads it is often the case that zone_reclaim_mode destroys performance but not all users know how to detect this. Favour the common case and disable it by default." Sounds good to me. Do you mind submitting a patch that prints a warning from either FileStore::_detect_fs()? That will appear in the local ceph-osd.NNN.log. Alternatively, we should send something to the cluster log (osd->clog.warning() << "...") but if we go that route we need to be careful that the logger it up and running first, which (I think) rules out FileStore::_detect_fs(). It could go in OSD itself although that seems less clean since the recommendation probably doesn't apply when using a backend that doesn't use a file system… Sure, I’ll try to prepare a patch which warns but isn’t too annoying. MongoDB already solved the heuristic: https://github.com/mongodb/mongo/blob/master/src/mongo/db/startup_warnings_mongod.cpp It’s licensed as AGPLv3 -- do you already know if we can borrow such code into Ceph? Cheers, Dan Thanks! sage
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