A file or volume (for example from ZFS or SVM) is exported either as a full disk or as single slice disk depending on whether or not the slice option is set.
If you do not set the slice option, a file or volume is exported as a full disk. In that case, virtual disk drivers (vds and vdc) forward I/O from the virtual disk and manage the partitioning of the virtual disk. The file or volume eventually becomes a disk image containing data from all slices of the virtual disk and the metadata used to manage the partitioning and disk structure.
When a blank file or volume is exported as full disk, it appears in the guest domain as an unformatted disk; that is, a disk with no partition. Then you need to run the format(1M) command in the guest domain to define usable partitions and to write a valid disk label. Any I/O to the virtual disk fails while the disk is unformatted.
Prior to the Solaris 10 5/08 OS release, when a blank file was exported as a virtual disk, the system wrote a default disk label and created default partitioning. This is no longer the case with the Solaris 10 5/08 OS release, and you must run format(1M) in the guest domain to create partitions.
From the service domain, create a file (fdisk0 for example) to use as the virtual disk.
service# mkfile 100m /ldoms/domain/test/fdisk0 |
The size of the file defines the size of the virtual disk. This example creates a 100- megabyte blank file to get a 100-megabyte virtual disk.
From the control domain, export the file as a virtual disk.
primary# ldm add-vdsdev /ldoms/domain/test/fdisk0 fdisk0@primary-vds0 |
In this example, the slice option is not set, so the file is exported as a full disk.
From the control domain, assign the disk to a guest domain.
For example, assign the disk (fdisk) to guest domain ldg1.
primary# ldm add-vdisk fdisk fdisk0@primary-vds0 ldg1 |
After the guest domain is started and running the Solaris OS, verify that the disk is accessible and is a full disk.
A full disk is a regular disk with 8 slices.
The following example shows how to list the disk, c0d5, and verify that it is accessible and is a full disk.
ldg1# ls -1 /dev/dsk/c0d5s* /dev/dsk/c0d5s0 /dev/dsk/c0d5s1 /dev/dsk/c0d5s2 /dev/dsk/c0d5s3 /dev/dsk/c0d5s4 /dev/dsk/c0d5s5 /dev/dsk/c0d5s6 /dev/dsk/c0d5s7 |
If the slice option is set, then the file or volume is exported as a single slice disk. In that case, the virtual disk has only one partition (s0), which is directly mapped to the file or volume backend. The file or volume only contains data written to the virtual disk with no extra data like partitioning information or disk structure.
When a file or volume is exported as a single slice disk, the system simulates a fake disk partitioning which makes that file or volume appear as a disk slice. Because the disk partitioning is simulated, you do not create partitioning for that disk.
Create a ZFS volume to use as a single slice disk.
The following example shows how to create a ZFS volume, zdisk0, to use as a single slice disk.
service# zfs create -V 100m ldoms/domain/test/zdisk0 |
The size of the volume defines the size of the virtual disk. This example creates a 100-megabyte volume to get a 100-megabyte virtual disk.
From the control domain, export the corresponding device to that ZFS volume, and set the slice option so that the volume is exported as a single slice disk.
primary# ldm add-vdsdev options=slice /dev/zvol/dsk/ldoms/domain/test/zdisk0 \ zdisk0@primary-vds0 |
From the control domain, assign the volume to a guest domain.
The following shows how to assign the volume, zdisk0, to guest domain ldg1.
primary# ldm add-vdisk zdisk0 zdisk0@primary-vds0 ldg1 |
After the guest domain is started and running the Solaris OS, you can list the disk (c0d9, for example) and see that the disk is accessible and is a single slice disk (s0).
ldg1# ls -1 /dev/dsk/c0d9s* /dev/dsk/c0d9s0 /dev/dsk/c0d9s1 /dev/dsk/c0d9s2 /dev/dsk/c0d9s3 /dev/dsk/c0d9s4 /dev/dsk/c0d9s5 /dev/dsk/c0d9s6 /dev/dsk/c0d9s7 |
Prior to the Solaris 10 5/08 OS release, the slice option did not exist, and volumes were exported as single slice disks. If you have a configuration exporting volumes as virtual disks and if you upgrade the system to the Solaris 10 5/08 OS, volumes are now exported as full disks instead of single slice disks. To preserve the old behavior and to have your volumes exported as single slice disks, you need to do either of the following:
Use the ldm set-vdsdev command in Logical Domains 1.3 software, and set the slice option for all volumes you want to export as single slice disks. Refer to the ldm(1M) man page for more information about this command.
Add the following line to the /etc/system file on the service domain.
set vds:vd_volume_force_slice = 1 |
Setting this tunable forces the export of all volumes as single slice disks, and you cannot export any volume as a full disk.
This section includes guidelines for exporting a file and a disk slice as a virtual disk.
It is possible to use the loopback file (lofi) driver to export a file as a virtual disk. However, doing this adds an extra driver layer and impacts performance of the virtual disk. Instead, you can directly export a file as a full disk or as a single slice disk. See File and Volume.
To export a slice as a virtual disk either directly or indirectly (for example through a SVM volume), ensure that the slice does not start on the first block (block 0) of the physical disk by using the prtvtoc(1M) command.
If you directly or indirectly export a disk slice which starts on the first block of a physical disk, you might overwrite the partition table of the physical disk and make all partitions of that disk inaccessible.