>>This page reads "If you set rbd_cache=true, you must set cache=writeback or risk data loss." ... Because if you don't set writeback in qemu, qemu don't send flush requests. And if you enable rbd cache, and your host is crashing, you'll lost datas and possible corrupt the filesystem. if you enable writeback,guest send flush request. If the host is crashing, you'll lost datas but it'll not corrupt the guest filesystem. ----- Mail original ----- De: "Blair Bethwaite" <blair.bethwaite@xxxxxxxxx> À: ceph-users@xxxxxxxxxxxxxx Envoyé: Jeudi 6 Février 2014 23:06:49 Objet: Re: RBD Caching - How to enable? Does anybody else think there is a problem with the docs/settings here... Message: 13 Date: Thu, 06 Feb 2014 12:11:53 +0100 (CET) From: Alexandre DERUMIER < aderumier@xxxxxxxxx > To: Graeme Lambert < glambert@xxxxxxxxxxx > Cc: ceph-users@xxxxxxxxxxxxxx Subject: Re: RBD Caching - How to enable? Message-ID: <d0af5e59-ea2a-471e-be65-ff273d0c0216@mailpro> Content-Type: text/plain; charset=utf-8 >>OK, so I need to change ceph.conf on the compute nodes? yes. >>Do the VMs using RBD images need to be restarted at all? I think yes. >>Anything changed in the virsh XML for the nodes? you need to add cache=writeback for your disks If you use qemu > 1.2, no need to add "rbd cache = true" to ceph .conf :) http://ceph.com/docs/next/rbd/qemu-rbd/ This page reads "If you set rbd_cache=true, you must set cache=writeback or risk data loss." ... That's an inverted definition of writeback AFAIK! -- Cheers, ~Blairo _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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