On Wed, Jul 18, 2018 at 12:36 PM Nikola Ciprich <nikola.cipr...@linuxbox.cz> wrote:
> ;6QHi Janon, > > > Just to clarify: modern / rebased krbd block drivers definitely support > > layering. The only missing features right now are object-map/fast-diff, > > deep-flatten, and journaling (for RBD mirroring). > > I thought it as well, but at least mapping clone does not work for me even > under 4.17.6: > > > [root@v4a ~]# rbd map nvme/xxx > rbd: sysfs write failed > RBD image feature set mismatch. You can disable features unsupported by > the kernel with "rbd feature disable nvme/xxx". > In some cases useful info is found in syslog - try "dmesg | tail". > rbd: map failed: (6) No such device or address > > (note incorrect hint on how this is supposed to be fixed, with feature > disable command without any feature) > > dmesg output: > > [ +3.919281] rbd: image xxx: WARNING: kernel layering is EXPERIMENTAL! > [ +0.001266] rbd: id 36dde238e1f29: image uses unsupported features: 0x38 > > > [root@v4a ~]# rbd info nvme/xxx > rbd image 'xxx': > size 20480 MB in 5120 objects > order 22 (4096 kB objects) > block_name_prefix: rbd_data.6a71313887ee0 > format: 2 > features: layering > flags: > create_timestamp: Wed Jun 20 13:46:38 2018 > parent: nvme/centos7@template > overlap: 20480 MB > > is trying 4.18-rc5 worth giving a try? > What's the output from "rbd info nvme/centos7"? > > If you are running multiple fio jobs against the same image (or have the > > krbd device mapped to multiple hosts w/ active IO), then I would expect a > > huge performance hit since the lock needs to be transitioned between > > clients. > > nope, only one running fio instance, no users on the other node.. > Odd. The exclusive-lock code is only executed once (in general) upon the first write IO (or immediately upon mapping the image if the "exclusive" option is passed to the kernel). Therefore, it should have zero impact on IO performance. > > BR > > nik > > > -- > ------------------------------------- > Ing. Nikola CIPRICH > LinuxBox.cz, s.r.o. > 28. rijna 168, 709 00 Ostrava > > tel.: +420 591 166 214 > fax: +420 596 621 273 > mobil: +420 777 093 799 > > www.linuxbox.cz > > mobil servis: +420 737 238 656 > email servis: ser...@linuxbox.cz > ------------------------------------- > -- Jason
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