On Thu, Nov 22, 2018 at 05:03:43PM +0100, Kashyap Chamarthy wrote: > On Fri, Oct 26, 2018 at 12:32:48PM +0100, lejeczek wrote: > > hi guys, > > > > anybody observed, maybe has measured performance difference between > > the two with qemu quests(windows OS)? > > > > Any conclusions, recommendations? > > [Cc Stefan from QEMU, probably he might have some pointers.] You can get good performance with qcow2 if you preallocate the image file: $ qemu-img create -f qcow2 -o preallocation=falloc vm001.qcow2 10G Writing to new regions of the image has a higher cost without preallocation. The downside is that the storage will be reserved for the disk image so you no longer start off with a tiny file that grows on demand. That's the trade-off if performance is critical. Stefan
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