librbd / QEMU advertise to the guest OS that the disk has writeback cache enabled so that the guest OS will send any necessary flush requests to inject write barriers and ensure data consistency. As a safety precaution, librbd will treat the cache as writethrough until it received the first flush request from the guest OS, at which point it will switch to writeback mode. Therefore, in general, it is safe to leave librbd configured to use writeback cache. Now if you disable the barriers in your guest OS or if you are running an application that doesn't properly sync its data as needed, then the librbd (or any) writeback cache cannot provide crash consistency and it might result in corruption. On Mon, Aug 8, 2016 at 4:29 AM, Ops Cloud <ops@xxxxxxxxxxx> wrote: > > Hello, > > I read from a blog article that with rbd cache open, it will influence the > data's consistency. > > is this true? for better consistency, should we disable rbd cache? > > thanks. > -- > Ops Cloud > ops@xxxxxxxxxxx > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- Jason _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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