>>> On 7/7/2015 at 02:03 PM, in message <559b6bbe.3050...@kamp.de>, Peter Lieven <p...@kamp.de> wrote: > Am 07.07.2015 um 07:59 schrieb Chun Yan Liu: > > > >>>> On 7/7/2015 at 01:50 PM, in message <559b68b2.5060...@kamp.de>, Peter > >>>> Lieven > > <p...@kamp.de> wrote: > >> Am 07.07.2015 um 03:50 schrieb Chun Yan Liu: > >>>>>> On 7/6/2015 at 06:42 PM, in message <559a5b79.4010...@kamp.de>, Peter > >>>>>> Lieven > >>> <p...@kamp.de> wrote: > >>>> Am 06.07.2015 um 11:44 schrieb Chun Yan Liu: > >>>>> While testing with a 1GB VHD file created on win7, found that the VHD > >>>>> file > >>>>> size reported on Windows is different from that is reported by qemu-img > >>>>> info or within a Linux KVM guest. > >>>>> > >>>>> Created a dynamic VHD file on win7, on Windows, it is reported 1024MB > >>>>> (2097152 sectors). But with qemu-img info or within a Linux KVM guest, > >>>>> it is reported 1023MB (2096640 sectors). > >>>>> > >>>>> The values in the footer_buf are as follows: > >>>>> creator_app: "win " > >>>>> cylinders: 0x820 (2080) > >>>>> heads: 0x10 (16) > >>>>> cyl/sec: 0x3f (63) > >>>>> current_size: 0x40000000 (1G) > >>>>> > >>>>> So, if using current_size, it's correct; but using CHS will get a > >>>>> smaller > >>>> size. > >>>>> Should we add a check in this case and use "current_size" instead of > >>>>> CHS? > >>>> > >>>> As far as I remember the issue was and still is that there is no > >>>> official > >>>> spec that says > >>>> use current_size in case A and CHS in case B. > >>> Understand. > >>> > >>>> > >>>> If currrent_size is greater than CHS and Windows would use CHS (we don't > >>>> know that) we might run into issues if Qemu uses current_size. In this > >>>> cas we would write data beyond the end of the container (from Windows > >>>> perspective). > >>> That's right. The fact is in our testing we found Windows does not use > >>> CHS > >>> but current_size (from testing result), we create and get the VHD parted > >>> on > >>> Windows, then take the VHD file into Linux KVM guest, it fails to show > >> partition > >>> table (since the reported disk size is shrinking, some of the partitions > >> extend > >>> beyond the end of the disk). > >> > >> Which version of Windows are you referring to? > > Tested with WS2012R2 and Win7. > > Which storage driver?
I'm not sure. See from "device management" -> "disk drive", it's named as "Msft virtual disk SCSI disk device", and from "storage controller", it has a separate controller named as "Microsoft VHD HBA". Anyway, seems not controlled by ATA/ATAPI. > > I had a look at the specs and in fact they more or less say: Use > current_size > and if you have an ATA controller derive the disk size from CHS. > > Peter > > >
