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Description of problem: convert qcow2/raw to vmdk with qemu-img on nfs file system, and save objective file to nfs file system. it write speed only 100k/second. Use the same method to convert other format image, conver rate is normal. e.g vmdk--->qcow2 vmdk--->raw Version-Release number of selected component (if applicable): qemu-kvm-1.5.2-3.el7.x86_64 3.10.0-11.el7.x86_64 How reproducible: 100% Steps to Reproduce: 1.mount nfs file system to local /mnt 2.time qemu-img convert -p -f qcow2 /mnt/rhel6.qcow2-O vmdk /mnt/rhel6-qcow2-vmdk 3. Actual results: convert rate only about 100k/sec Expected results: ~40M Additional info: If objective file don't save on nfs file system, convert rate is good.
Posted a patch to upstream: http://patchwork.ozlabs.org/patch/340295/
Fix included in qemu-kvm-1.5.3-84.el7
Reproduced this bug with qemu-kvm-1.5.3-83.el7.x86_64 Steps: 1.Prepare a 3.2G actually size qcow2 image which is in nfs server. # qemu-img info /mnt/rhel7/rhel7base.qcow2 image: /mnt/rhel7/rhel7base.qcow2 file format: qcow2 virtual size: 30G (32212254720 bytes) disk size: 3.2G cluster_size: 65536 Format specific information: compat: 1.1 lazy refcounts: false 2.Try to convert it to be vmdk format. # time qemu-img convert -p -f qcow2 /mnt/rhel7/rhel7base.qcow2 -O vmdk /mnt/test2.vmdk Result: # time qemu-img convert -p -f qcow2 /mnt/rhel7/rhel7base.qcow2 -O vmdk /mnt/test2.vmdk (100.00/100%) real 79m0.067s user 0m4.741s sys 0m26.629s The speed is 675k/s, so this bug is reproduced. Verified this bug with qemu-kvm-1.5.3-84.el7.x86_64 and qemu-kvm-rhev-2.1.2-17.el7.x86_64 Steps as above Results: 1.With qemu-kvm-1.5.3-84.el7.x86_64 # time qemu-img convert -p -f qcow2 /mnt/rhel7/rhel7base.qcow2 -O vmdk /mnt/test1.vmdk (100.00/100%) real 1m46.145s user 0m3.416s sys 0m15.311s The speed is 32M/s 2.With qemu-kvm-rhev-2.1.2-17.el7.x86_64 # time qemu-img convert -p -f qcow2 /mnt/rhel7/rhel7base.qcow2 -O vmdk /mnt/test2.vmdk (0.00/100%) (100.00/100%) real 1m29.221s user 0m2.212s sys 0m4.666s The speed is 36M/s The speed is acceptable, so this bug is fixed by qemu-kvm-rhev-2.1.2-17.el7.x86_64 and qemu-kvm-1.5.3-84.el7.x86_64
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHSA-2015-0349.html