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. _______________________________________________ virt mailing list [email protected] https://admin.fedoraproject.org/mailman/listinfo/virt
