Description of problem:
We recommend running qemu with 'cache=none' for block devices. Set the default to 'cache=none' so that libvirt, vdsm, virt-manager, cmd-line users, all don't have to explicitly do that.
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release. Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
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Upstream now has cache=writeback as the default. However, this is a non-issue for RHEL since we always go through libvirt.