On Mon, Aug 19, 2013 at 9:07 AM, Sage Weil <sage@xxxxxxxxxxx> wrote: > On Mon, 19 Aug 2013, S?bastien Han wrote: >> Hi guys, >> >> While reading a developer doc, I came across the following options: >> >> * osd balance reads = true >> * osd shed reads = true >> * osd shed reads min latency >> * osd shed reads min latency diff >> >> The problem is that I can't find any of these options in config_opts.h. > > These are left over from an old unimplemented experiment and were removed > a while back. > >> Loic Dachary also gave me a flag that he found from the code. >> >> m->get_flags() & CEPH_OSD_FLAG_LOCALIZE_READS) >> >> So my questions are: >> >> * Which from the above flags are correct? >> * Do balanced reads really exist in RBD? > > For localized reads you want > > OPTION(rbd_balance_snap_reads, OPT_BOOL, false) > OPTION(rbd_localize_snap_reads, OPT_BOOL, false) > > Note that the 'localize' logic is still very primitive (it matches by IP > address). There is a blueprint to improve this: > > http://wiki.ceph.com/01Planning/02Blueprints/Emperor/librados%2F%2Fobjecter%3A_smarter_localized_reads Also, there are some issues with read/write consistency when using localized reads because the replicas do not provide the ordering guarantees that primaries will. See http://tracker.ceph.com/issues/5388 At present localized reads are really only suitable for spreading the load on write-once, read-many workloads. -Greg Software Engineer #42 @ http://inktank.com | http://ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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