Hello, how did you come up with those bizarre cache sizes? Either way, if you test with FIO anything that will significantly exceed the size of the cache will have very little to no effect. To verify things, set the cache values to be based around 2GB and test with a FIO that is just 1GB in size. This will also increase the memory footprint of your VM (if you run enough tests) to that of its memory limits PLUS the cache, verifying that the cache is actually on. RBD caching works well with the default sizes for small, bursty IOs. Christian On Tue, 8 Jul 2014 21:08:49 +0800 (CST) lijian wrote: > Haomai Wang, > > I use the FIO to test 4K and 1M read/write under iodepth=1 and > iodepth=32 in VM Do you know the improvements percentage using cache > base on yourself test. > > Thanks! > JIan Li > > At 2014-07-08 08:47:39, "Haomai Wang" <haomaiwang at gmail.com> wrote: > >With info you provided, I think you have enabled rbd cache. As for > >performance improvement, it's related to your performance tests > > > >On Tue, Jul 8, 2014 at 8:34 PM, lijian <blacker1981 at 163.com> wrote: > >> Hello, > >> > >> I want to enable the qemu rbd writeback cache, the following is the > >> settings in /etc/ceph/ceph.conf > >> [client] > >> rbd_cache = true > >> rbd_cache_writethrough_until_flush = false > >> rbd_cache_size = 27180800 > >> rbd_cache_max_dirty = 20918080 > >> rbd_cache_target_dirty = 16808000 > >> rbd_cache_max_dirty_age = 60 > >> > >> and the next section is the vm definition xml: > >> <disk type='network' device='disk'> > >> <driver name='qemu' cache='writeback'/> > >> <auth username='estack'> > >> <secret type='ceph' > >> uuid='101ae7dc-bd59-485e-acba-efc8ddbe0d01'/> </auth> > >> <source protocol='rbd' name='estack/new-libvirt-image'> > >> <host name='X.X.X.X' port='6789'/> > >> </source> > >> <target dev='vdb' bus='virtio'/> > >> <address type='pci' domain='0x0000' bus='0x00' slot='0x07' > >> function='0x0'/> > >> </disk> > >> > >> my host OS is Ubuntu, kernel 3.11.0-12-generic, the kvm-qemu is > >> 1.5.0+dfsg-3ubuntu5.4, the guest os is Ubuntu 13.11 > >> ceph version is 0.80.1 (a38fe1169b6d2ac98b427334c12d7cf81f809b74) > >> > >> no performance improvements using the above cache settings, So what's > >> wrong with me, please help, thanks! > >> > >> Jian Li > >> > >> > >> > >> _______________________________________________ > >> ceph-users mailing list > >> ceph-users at lists.ceph.com > >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > >> > > > > > > > >-- > >Best Regards, > > > >Wheat -- Christian Balzer Network/Systems Engineer chibi at gol.com Global OnLine Japan/Fusion Communications http://www.gol.com/
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