Fix included in qemu-kvm-rhev-2.1.2-10.el7

Reproduce this bug as follow version:

# uname -r
3.10.0-210.el7.x86_64
# rpm -q qemu-kvm-rhev
qemu-kvm-rhev-2.1.2-8.el7.x86_64

Steps:
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

Results:
# time qemu-img convert -p -f qcow2 /mnt/RHEL-Server-6.6-64-virtio.qcow2 -O vmdk /mnt/rhel6-qcow2-vmdk
^C  (2.03/100%)

real	2m13.521s
user	0m0.452s
sys	0m1.372s

#ll -lh  rhel6-qcow2-vmdk
-rw-r--r--. 1 root root 125M Nov 28 16:12 rhel6-qcow2-vmdk

About 948k/s


Verify this bug as follow version:
Host:
# uname -r
3.10.0-210.el7.x86_64
# rpm -q qemu-kvm-rhev
qemu-kvm-rhev-2.1.2-13.el7.x86_64

Steps:

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


Results:
[root@localhost mnt]# time qemu-img convert -p -f qcow2 /mnt/RHEL-Server-6.6-64-virtio.qcow2 -O vmdk /mnt/rhel6-qcow2-vmdk
    (100.00/100%)

real	2m15.210s
user	0m2.960s
sys	0m7.313s

#ll -lh rhel6-qcow2-vmdk
-rw-r--r--. 1 root root 7G Nov 28 16:12 rhel6-qcow2-vmdk

About 50M/s


Addtional test :raw-->vmdk

time qemu-img convert -p -f raw /mnt/RHEL-Server-7.1-64-virtio.raw -O vmdk /mnt/rhel6-qcow2-vmdk

Results:100M/s


According to above test ,this bug has been fixed.

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-2015-0624.html