Just for the sake of putting this in the public forum, In theory, by placing the primary copy of the object on an SSD medium, and placing replica copies on HDD medium, it should still yield some improvement in writes, compared to an all HDD scenario.
My logic here is rooted in the idea that the first copy requires a write, ACK, and then a read to send a copy to the replicas. So instead of a slow write, and a slow read on your first hop, you have a fast write and fast read on the first hop, before pushing out to the slower second hop of 2x slow writes and ACKs. Doubly so, if you have active io on the cluster, the SSD is taking all of the read io away from the slow HDDs, freeing up iops on the HDDs, which in turn should clear write ops quicker. Please poke holes in this if you can. Hopefully this will be useful for someone searching the ML. Thanks, Reed > On Oct 10, 2017, at 6:50 PM, Christian Balzer <ch...@gol.com> wrote: > > All writes have to be ACKed, the only time where hybrid stuff helps is to > accelerate reads. > Which is something that people like me at least have very little interest > in as the writes need to be fast. > > Christian > >> (the same setup could involve some high latency OSDs, in the case of >> country-level cluster) >> _______________________________________________ >> ceph-users mailing list >> ceph-users@lists.ceph.com >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> > > > -- > Christian Balzer Network/Systems Engineer > ch...@gol.com Rakuten Communications > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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