On 12/11/15 09:37, Gregory Farnum wrote: > On Wednesday, November 11, 2015, Wido den Hollander <wido@xxxxxxxx > <mailto:wido@xxxxxxxx>> wrote: > > On 11/10/2015 09:49 PM, Vickey Singh wrote: > > On Mon, Nov 9, 2015 at 8:16 PM, Wido den Hollander <wido@xxxxxxxx > <javascript:;>> wrote: > > > >> On 11/09/2015 05:27 PM, Vickey Singh wrote: > >>> Hello Ceph Geeks > >>> > >>> Need your comments with my understanding on straw2. > >>> > >>> - Is Straw2 better than straw ? > >> > >> It is not persé better then straw(1). > >> > >> straw2 distributes data better when not all OSDs are equally > >> sized/weighted. > >> > >>> - Is it straw2 recommended for production usage ? > >>> > >> > >> I'm using it in multiple clusters and it works fine. > >> > > > > Yes i followed your update on twitter :) > > > > > >> > >>> I have a production Ceph Firefly cluster , that i am going to > upgrade to > >>> Ceph hammer pretty soon. Should i use straw2 for all my ceph pools ? > >>> > >> > >> I would upgrade to Hammer first and make sure that ALL clients > are updated. > >> > >> In case you are using KVM/Qemu, you will have to stop those processes > >> first and start them again before they are using the new code. > >> > > > > Thanks a lot for this pointer, i didn't knew this. So restarting > KVM / QEMU > > process effect running VMs ? ( some downtime ) > > > > Yes. You can also (live) migrate to another host since that will spawn > Qemu with fresh code on the other host. > > But you have to make sure all running/connected clients support straw2 > before you enable straw2. > > > I believe straw2 only requires monitor support -- unlike the tuna led > involved in executing CRUSH, straw2 is just about how the OSD/bucket > weights get converted into a sort of "internal" straw weight. That's > done on the monitors and encoded into the maps. > > Right? > -Greg I don't believe that's the case. If you convert a CRUSH map to use straw2 then any connected QEMU/librbd clients without straw2 support will die with something like: terminate called after throwing an instance of 'ceph::buffer::malformed_input' what(): buffer::malformed_input: unsupported bucket algorithm: 5 Where: ceph/src/crush/crush.h:CRUSH_BUCKET_STRAW2 = 5, -- David Clarke Systems Architect Catalyst IT
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