On Fri, 6 Jun 2014, zou wonder wrote: > Hi Wido: > > Thanks for your kindness, i checked the codes just now, seems there > were no overload related thing in CRUSH codes. It is a little bit not > consistent with the CRUSH paper. > So if the %100 utilized OSD is returned, the objects will still be > written on the underlined storage device? The 'overload' discussion in the CRUSH paper corresonds to the ceph osd reweight-by-utilization command, which looks at disk utilizations and adjusts the osd reweight values to divert some mappings away from OSDs with significantly above-average utilizations. This tightens up the statistical variance in utilizations across devices. sage > > How about the device failure case? All the objects on the failure > device will be replicated to the good ones? once the device is > recoverd, the data will be replicated back? > > Best Regards > Zou > > On Fri, Jun 6, 2014 at 4:27 PM, Wido den Hollander <wido@xxxxxxxx> wrote: > > On 06/06/2014 10:14 AM, zou wonder wrote: > >> > >> Hi buddies, > >> > >> I am doing investigation on Ceph and Swift,and I am newbie to Ceph. > >> > >> I am unclear to the behaviour of the Ceph when there is overload > >> situation. > >> According to the doc, when Ceph do CRUSH, if it find the OSD is overload, > >> it will skip it to select the other OSD. It means if the OSD don't get > >> overloaded > >> the object should be put in this OSD. So how about the original on put on > >> this OSD when it is not get overloaded? > >> Can we read it ? When doing CRUSH , the OSD will be skip. > >> > > > > CRUSH will not take any performance characteristics into account. If a OSD > > is 100% utilized it will still be selected by CRUSH. > > > > Keep in mind however that Block Devices are striped in 4MB chunks and the > > same happens for Objects stored via the RADOS Gateway. > > > >> If my understanding is wrong, please correct me. > >> > >> Best Regards, > >> zou > >> -- > >> 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 > >> > > > > > > -- > > Wido den Hollander > > 42on B.V. > > Ceph trainer and consultant > > > > Phone: +31 (0)20 700 9902 > > Skype: contact42on > -- > 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 > > -- 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
