It sounds like maybe you're using Xen? The "rbd writeback window" option only works for userspace rbd implementations (eg, KVM). If you are using KVM, you probably want 81920000 (~80MB) rather than 8192000 (~8MB). What options are you running dd with? If you run a rados bench from both machines, what do the results look like? Also, can you do the ceph osd bench on each of your OSDs, please? (http://ceph.newdream.net/wiki/Troubleshooting#OSD_performance) -Greg On Monday, March 19, 2012 at 6:46 AM, Andrey Korolyov wrote: > More strangely, writing speed drops down by fifteen percent when this > option was set in vm` config(instead of result from > http://www.mail-archive.com/ceph-devel@xxxxxxxxxxxxxxx/msg03685.html). > As I mentioned, I`m using 0.43, but due to crashed osds, ceph has been > recompiled with e43546dee9246773ffd6877b4f9495f1ec61cd55 and > 1468d95101adfad44247016a1399aab6b86708d2 - both cases caused crashes > under heavy load. > > On Sun, Mar 18, 2012 at 10:22 PM, Sage Weil <sage@xxxxxxxxxxxx (mailto:sage@xxxxxxxxxxxx)> wrote: > > On Sat, 17 Mar 2012, Andrey Korolyov wrote: > > > Hi, > > > > > > I`ve did some performance tests at the following configuration: > > > > > > mon0, osd0 and mon1, osd1 - two twelve-core r410 with 32G ram, mon2 - > > > dom0 with three dedicated cores and 1.5G, mostly idle. First three > > > disks on each r410 arranged into raid0 and holds osd data when fourth > > > holds os and osd` journal partition, all ceph-related stuff mounted on > > > the ext4 without barriers. > > > > > > Firstly, I`ve noticed about a difference of benchmark performance and > > > write speed through rbd from small kvm instance running on one of > > > first two machines - when bench gave me about 110Mb/s, writing zeros > > > to raw block device inside vm with dd was at top speed about 45 mb/s, > > > for vm`fs (ext4 with default options) performance drops to ~23Mb/s. > > > Things get worse, when I`ve started second vm at second host and tried > > > to continue same dd tests simultaneously - performance fairly divided > > > by half for each instance :). Enabling jumbo frames, playing with cpu > > > affinity for ceph and vm instances and trying different TCP congestion > > > protocols gave no effect at all - with DCTCP I have slightly smoother > > > network load graph and that`s all. > > > > > > Can ml please suggest anything to try to improve performance? > > > > Can you try setting > > > > rbd writeback window = 8192000 > > > > or similar, and see what kind of effect that has? I suspect it'll speed > > up dd; I'm less sure about ext3. > > > > Thanks! > > sage > > > > > > > > > > ceph-0.43, libvirt-0.9.8, qemu-1.0.0, kernel 3.2 > > > -- > > > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > > > the body of a message to majordomo@xxxxxxxxxxxxxxx (mailto:majordomo@xxxxxxxxxxxxxxx) > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx (mailto:majordomo@xxxxxxxxxxxxxxx) > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
