=head1 SYNOPSIS
- virt-alignment-scan [--options]
-
virt-alignment-scan [--options] -d domname
virt-alignment-scan [--options] -a disk.img [-a disk.img ...]
New versions of the Linux kernel expose the physical and logical block
size, and minimum and recommended I/O size.
-For a typical hard drive with 512 byte sectors:
+For a typical consumer hard drive with 512 byte sectors:
+ $ cat /sys/block/sda/queue/hw_sector_size
+ 512
$ cat /sys/block/sda/queue/physical_block_size
512
$ cat /sys/block/sda/queue/logical_block_size
$ cat /sys/block/sda/queue/optimal_io_size
0
+For a new consumer hard drive with 4Kbyte sectors:
+
+ $ cat /sys/block/sda/queue/hw_sector_size
+ 4096
+ $ cat /sys/block/sda/queue/physical_block_size
+ 4096
+ $ cat /sys/block/sda/queue/logical_block_size
+ 4096
+ $ cat /sys/block/sda/queue/minimum_io_size
+ 4096
+ $ cat /sys/block/sda/queue/optimal_io_size
+ 0
+
For a NetApp LUN:
$ cat /sys/block/sdc/queue/logical_block_size
For detailed information about what these numbers mean, see
L<http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/newstorage-iolimits.html>
-[Thanks to Mike Snitzer for providing NetApp data and additional
-information.]
+[Thanks to Matt Booth for providing 4K drive data. Thanks to Mike
+Snitzer for providing NetApp data and additional information.]
=head2 1 MB PARTITION ALIGNMENT
=head2 SETTING ALIGNMENT
-Currently there is no virt tool for fixing alignment problems in
-guests. This is a difficult problem to fix because simply moving
-partitions around breaks the bootloader, necessitating either manual
-reinstallation of the bootloader using a rescue disk, or complex and
-error-prone hacks.
-
-L<virt-resize(1)> does not change the alignment of the first
-partition, but it does align the second and subsequent partitions to a
-multiple of 64 or 128 sectors (depending on the version of
-virt-resize, 128 in virt-resize E<ge> 1.13.19). For operating systems
-that have a separate boot partition, virt-resize could be used to
-align the main OS partition, so that the majority of OS accesses
-except at boot will be aligned.
-
-The easiest way to correct partition alignment problems is to
-reinstall your guest operating systems. If you install operating
-systems from templates, ensure these have correct partition alignment
-too.
+L<virt-resize(1)> can change the alignment of the partitions of some
+guests. Currently it can fully align all the partitions of all
+Windows guests, and it will fix the bootloader where necessary. For
+Linux guests, it can align the second and subsequent partitions, so
+the majority of OS accesses except at boot will be aligned.
+
+Another way to correct partition alignment problems is to reinstall
+your guest operating systems. If you install operating systems from
+templates, ensure these have correct partition alignment too.
For older versions of Windows, the following NetApp document contains
useful information: L<http://media.netapp.com/documents/tr-3747.pdf>
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
-Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.