[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-users] Disk IO tuning
On Fri, Dec 16, 2011 at 4:27 AM, Andrew Wells <agwells0714@xxxxxxxxx> wrote: > So with the the pv > > My writes are alright, could be better, > > but my reads are really slow compared to the hardware system? > Any hints for tuning the pv disk io? How did you measure "really slow"? Are you sure it's not the effect of cache? I suggest you try again using block device directly (without filesystem). For example, this is on my system (RHEL6 + xen-4.1.1+ kernel 3.1.0 + zfs), testing using "dd_rescue -d -b128k -B128k -m128M /path/of/block/device/tested /dev/null", testing the same block device in three scenario: - on dom0 directly: got about 22 MBps (yes, this is pretty slow. I only have two disks, mirrored). - on dom0, but with block device mapped to dom0 with "xm block-attach" (not sure what the equivalent command is in xen server): about 18 MBps - on PV domU: about 18 MBps the "-d" flag to dd_rescue opens the block device using O_DIRECT, to avoid cache skewing up the result. -- Fajar _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users
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