Hello, On Mon, 29 Dec 2014 13:49:49 +0400 Andrey Korolyov wrote:
> On Mon, Dec 29, 2014 at 12:47 PM, Tomasz Kuzemko > <tomasz.kuze...@ovh.net> wrote: > > On Sun, Dec 28, 2014 at 02:49:08PM +0900, Christian Balzer wrote: > >> You really, really want size 3 and a third node for both performance > >> (reads) and redundancy. > > > > How does it benefit read performance? I thought all reads are made only > > from the active primary OSD. > > > > -- > > Tomasz Kuzemko > > tomasz.kuze...@ovh.net > > You`ll have chunks of primary data scattered between three devices > instead of two, as each pg will have a random acting set (until you > decide to pin primary). > What Andrey wrote. Reads will scale up (on a cluster basis, individual clients might not benefit as much) linearly with each additional "device" (host/OSD). Writes will scale up with each additional device divided by replica size. Fun fact, if you have 1 node with replica 1 and add 2 more identical nodes and increase the replica to 3, your write performance will be less than 50% of the single node. Once you add a 4th node, write speed will increase again. Christian -- Christian Balzer Network/Systems Engineer ch...@gol.com Global OnLine Japan/Fusion Communications http://www.gol.com/ _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
