Libguestfs - Jun 2012 - [virt-tools-list] virt-make-fs: Partition 1 has different physical/logical beginnings and endings

On Thu, Jun 07, 2012 at 02:49:14PM +0200, Sebastien Douche
wrote:
> On Ubuntu 12.04, I'm trying to create a second disk for a VM. The disk
> seems work well (and mounted) but I don't like the cfdisk / fdisk
> message.
> 
> # virt-make-fs --partition --size=+300M --type=ext3 --format=qcow2
> srv-2912.tar.gz datadisk-test.qcow2
> Formatting 'datadisk-test.qcow2', fmt=qcow2 size=393837568
> encryption=off cluster_size=65536
> 
> # virt-filesystems -a datadisk-test.qcow2
> /dev/sda1
> 
> I add the disk on the VM:
> 
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='qcow2'
cache='none'/>
>       <source file='/srv/kvm/lib/datadisk-test.qcow2'/>
>       <target dev='hdb' bus='ide'/>
>       <address type='drive' controller='0'
bus='1' unit='0'/>
>     </disk>
> 
> 
> The dmesg seems good :
> 
> [    1.404447] scsi 1:0:0:0: Direct-Access     ATA      QEMU HARDDISK
>   1.0  PQ: 0 ANSI: 5
> [    1.545945] sd 0:0:0:0: [sda] 8388608 512-byte logical blocks:
> (4.29 GB/4.00 GiB)
> [    1.554467] sd 1:0:0:0: [sdb] 769214 512-byte logical blocks: (393
> MB/375 MiB)
> [    1.555975] sd 1:0:0:0: [sdb] Write Protect is off
> [    1.556943] sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
> [    1.556969] sd 1:0:0:0: [sdb] Write cache: enabled, read cache:
> enabled, doesn't support DPO or FUA
> [    1.559923]  sdb:
> [    1.560603] sd 0:0:0:0: [sda] Write Protect is off
> [    1.561837] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
> [    1.561864] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
> enabled, doesn't support DPO or FUA
> [    1.563637]  sda: sdb1
> 
> But fdisk said :
> 
> Command (m for help): p
> 
> Disk /dev/sdb: 393 MB, 393837568 bytes
> 223 heads, 46 sectors/track, 74 cylinders
> Units = cylinders of 10258 * 512 = 5252096 bytes
> Disk identifier: 0x0002345e
> 
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sdb1               1          75      384479+  83  Linux
> Partition 1 has different physical/logical beginnings (non-Linux?):
>      phys=(0, 2, 3) logical=(0, 2, 37)
> Partition 1 has different physical/logical endings:
>      phys=(47, 222, 46) logical=(74, 217, 13)
> 
> And cfdisk:
> FATAL ERROR: Bad primary partition 0: Partition ends in the final
> partial cylinder
> 
> Have I missed something? Any ideas?
This is caused because virtio (used by libguestfs) and the IDE
emulation (used by your VM) guess different CHS values for this disk.

To be honest I would simply ignore this warning, since CHS values
don't matter for virtual machine disks.  If you really want to fix it,
you could modify your guest to use virtio-blk, which will also make
the guest run much faster.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org

On Thu, Jun 7, 2012 at 6:12 PM, Richard W.M. Jones <rjones at redhat.com>
wrote:
> This is caused because virtio (used by libguestfs) and the IDE
> emulation (used by your VM) guess different CHS values for this disk.
>
> To be honest I would simply ignore this warning, since CHS values
> don't matter for virtual machine disks. ?If you really want to fix it,
> you could modify your guest to use virtio-blk, which will also make
> the guest run much faster.
Thanks for the clarification Richard.

-- 
Sebastien Douche <sdouche at gmail.com>
Twitter: @sdouche / G+: +sdouche