On Fri, 12 Jun 2015 10:18:18 -0500 Mark Nelson wrote: > If you are careful about how you balance things, there's probably no > reason why SSDs and Spinners in the same server wouldn't work so long as > they are not in the same pool. I imagine that recommendation is > probably to keep things simple and have folks avoid designing unbalanced > systems. > Precisely. A mixed system needs a VERY intimate knowledge of Ceph and you work load, use case. SSD based OSDs will use a lot more CPU, saturate a lot more network bandwidth that HDD based ones. And putting 2.5" SSDs into 3.5" bays is a waste of (rack) space. As an example, a 2U server with 12 3.5" bays (OSDs) and 2 2.5" bays (OS and journals)in the back (hello Supermicro) makes a good, dense spinning rust based storage node. This will saturate about 10Gb/s In the same 2U you can have a twin node (2x 12 2.5" bays), with 8-10 SSDs per node and the fastest CPUs you can afford, as well as the fasted network (dual 10Gb/s or faster) that your budget allows. Christian > Mark > > On 06/12/2015 10:06 AM, Quentin Hartman wrote: > > I don't know the official reason, but I would imagine the disparity in > > performance would lead to weird behaviors and very spiky overall > > performance. I would think that running a mix of SSD and HDD OSDs in > > the same pool would be frowned upon, not just the same server. > > > > On Fri, Jun 12, 2015 at 9:00 AM, Dominik Zalewski > > <dzalewski@xxxxxxxxxxxxx <mailto:dzalewski@xxxxxxxxxxxxx>> wrote: > > > > Be warned that running SSD and HD based OSDs in the same server > > is not > > recommended. If you need the storage capacity, I'd stick to the > > journals > > on SSDs plan. > > > > > > Can you please elaborate more why running SSD and HD based OSDs in > > the same server is not > > recommended ? > > > > Thanks > > > > Dominik > > > > _______________________________________________ > > ceph-users mailing list > > ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx> > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > > > > > > > > _______________________________________________ > > ceph-users mailing list > > ceph-users@xxxxxxxxxxxxxx > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- Christian Balzer Network/Systems Engineer chibi@xxxxxxx Global OnLine Japan/Fusion Communications http://www.gol.com/ _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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