[fedora-virt] virtio cache mode and windows XP bluescreens
I saw a thread a month or so ago on disk performance, and
just for grins, I thought I'd try different disk cache settings
for my Windows XP virtual machine that has a qcow2 image
file (I know qcow2 is never going to be really fast, but I
thought I'd see if I could get any improvement at all).
Every cache mode I tried (changing them in the advanced
options of the hardware viewer screen in virt-manager) resulted
in the XP machine getting into a bluescreen loop when I booted
it.
Finally set it back to "default" and the XP machine stopped
getting bluescreens.
Are other cache modes supposed to work OK? Should I
report a bug on some component? Should I try and capture
the bluescreen content? (It flickers in and out really fast).
The main reason I was trying this is because it sure seems
like the qcow2 image gets slower and slower every time I
upgrade fedora and get new and improved qemu and libvirt
code. I don't have solid benchmarks, but it sure feels
slower. Has optimization of cases that are supposed to be fast
slowed down qcow2 somehow?
I'm currently trying to build an updated base image by
doing the trick of writing a giant file of zeros to fill
up the disk so I can then convert the mostly zero image to
a new qcow2 file, and the rate it is going makes it seem like
it may well be tomorrow before it finishes writing the
10 GB or so of zeros it needs to finish filling up the
disk image.
None of my CPUs are showing over 1% utilization and gkrellm
is showing only 2.0M disk write rate, so it sure seems like
all the components involved are spending more time just
waiting than anything else.