[fedora-arm] Write-back vs. write-through for VMs

I've been using the vexpress image with QEMU to try to track down some
ARM-specific problems in two of my packages. The VM was unbearably
slow at first (by which I mean that a simple "yum upgrade" took over 6
hours), until I changed:

-sd "$IMAGE"

to:

-drive if=sd,cache=writeback,file="$IMAGE"

in boot-vexpress and boot-vexpress+x. I'm well aware of the danger of
using writeback, but ... it's a VM. With the script as shipped, my
hard drive light was on constantly, and the entire host was slowed
down dramatically due to insufficient disk bandwidth. With writeback
on, I can re-create the VM and reinstall the packages of interest in
very little time, certainly less than even simple operations were
taking with write-through on. Is there some reason why changing the
scripts to use writeback would not be a good idea?

Regards,
--
Jerry James
http://www.jamezone.org/
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