Re: [libvirt] [Qemu-block] [RFC] finegrained disk driver options control

> OK. How could I change L2 cache size for QCOW2 image? > > For 1 Tb disk, fragmented in guest, the performance loss is > around 10 times. 10 TIMES. 1000%. The customer could not > wait until proper fix in the next QEMU release especially > if we are able to provide the kludge specifically for him. We can explicitly allow L2 cache size set in the XML but that is a pretty poor solution to the problem IMHO, as the mgmt application has no apriori knowledge of whether a particular cache size is going to be right for a particular QCow2 image. For a sustainable solution, IMHO this really needs to be fixed in QEMU so it has either a more appropriate default, or if a single default is not possible, have QEMU auto-tune its cache size dynamically to suit the characteristics of the qcow2 image.