On Thu, May 17, 2012 at 2:27 PM, Gregory Farnum <greg@xxxxxxxxxxx> wrote: > Sorry this got left for so long... > > On Thu, May 10, 2012 at 6:23 AM, Stefan Priebe - Profihost AG > <s.priebe@xxxxxxxxxxxx> wrote: >> Hi, >> >> the "Designing a cluster guide" >> http://wiki.ceph.com/wiki/Designing_a_cluster is pretty good but it >> still leaves some questions unanswered. >> >> It mentions for example "Fast CPU" for the mds system. What does fast >> mean? Just the speed of one core? Or is ceph designed to use multi core? >> Is multi core or more speed important? > Right now, it's primarily the speed of a single core. The MDS is > highly threaded but doing most things requires grabbing a big lock. > How fast is a qualitative rather than quantitative assessment at this > point, though. > >> The Cluster Design Recommendations mentions to seperate all Daemons on >> dedicated machines. Is this also for the MON useful? As they're so >> leightweight why not running them on the OSDs? > It depends on what your nodes look like, and what sort of cluster > you're running. The monitors are pretty lightweight, but they will add > *some* load. More important is their disk access patterns — they have > to do a lot of syncs. So if they're sharing a machine with some other > daemon you want them to have an independent disk and to be running a > new kernel&glibc so that they can use syncfs rather than sync. (The > only distribution I know for sure does this is Ubuntu 12.04.) I just had it pointed out to me that I rather overstated the importance of syncfs if you were going to do this. The monitor mostly does fsync, not sync/syncfs(), so that's not so important. What is important is that it has highly seeky disk behavior, so you don't want a ceph-osd and ceph-mon daemon to be sharing a disk. :) -Greg -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
