On Thu, Sep 17, 2015 at 7:55 AM, Corin Langosch <corin.lango...@netskin.com> wrote: > Hi Greg, > > Am 17.09.2015 um 16:42 schrieb Gregory Farnum: >> Briefly, if you do a lot of small direct IOs (for instance, a database >> journal) then striping lets you send each sequential write to a >> separate object. This means they don't pile up behind each other >> grabbing write locks and can complete in parallel. Striping them >> instead of just having small block-sized objects means the objects are >> still of a reasonable size for RADOS. >> > > Sounds good - why not enabled it always/ by default? Is the only drawback > that there's no support by kernel rbd? What's the recommended stripe size > for "normal" qemu workloads? 64k?
If you're doing large streaming writes then having to split them up across multiple objects is slower. It's just a knob you can twirl depending on the workload of the machine using this disk. > >> I *think* that's just because the features are only filled in if >> they're in use (the kernel doesn't/didn't support striping, despite >> supporting other V2 image features) and required to understand the >> image, but maybe I'm misunderstanding you or forgetting how the RBD >> team set things up. > > That doesn't seem to be the case. When I use librbd direcly (for example > using ceph-ruby) the feature is immediately visible, just as all other > features. Dunno then, Josh or Jason maybe? _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
