Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 10/26/2011 10:48 AM, Markus Armbruster wrote: >> Sector size is a device property. >> >> If the user asks for a 4K sector disk, and the backend can't support >> that, we need to reject the configuration. Just like we reject >> read-only backends for read/write disks. > > Isn't it the other way round, i.e. the user asks for a 512-byte sector > disk (i.e. the default) with cache=none but the disk has 4k sectors? Let me rephrase: If the user asks for a FOO disk, and the backend can't support that, we need to reject the configuration. Just like we reject read-only backends for read/write disks. > We're basically saying "choose between NFS and migration if you have > 4k sector disks but your guest doesn't support them". Understandable > perhaps, but not exactly kind, and virtualization is also about > shielding from this kind of hardware dependency even at the cost of > performance. QEMU should just warn about performance degradations, > erroring out would be a policy decision that should be up to > management. I don't have strong opinions on that. >> It's okay to default device properties to some backend-dependent value, >> if that improves usability. > > On the other hand, not all guests support 4k-sectors properly. You can't pick perfect defaults for all conceivable guests. Life's tough. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
