Automatic Disk Partitioning

When you add a new disk to a disk set, Solaris Volume Manager checks the disk format. If necessary, Solaris Volume Manager repartitions the disk to ensure that the disk has an appropriately configured slice 7 with adequate space for a state database replica. The precise size of slice 7 depends on the disk geometry. However, the size will be no less than 4 Mbytes, and probably closer to 6 Mbytes (depending on where the cylinder boundaries lie).

By default, Solaris Volume Manager places one state database replica on slice 7. You can increase the default size of slice 7 or decrease the size of the state database replica in order to fit more than one state database replica onto the slice.

The minimal size for slice 7 will likely change in the future, based on a variety of factors, including the size of the state database replica and information to be stored in the state database replica. The default size for a state database replica in a multi-owner disk set is 16 Mbytes.

For use in disk sets, disks must have a slice 7 that meets these criteria:

• Starts at sector 0

• Includes enough space for a disk label and state database replicas

• Cannot be mounted

• Does not overlap with any other slices, including slice 2

If the existing partition table does not meet these criteria, Solaris Volume Manager repartitions the disk. A small portion of each drive is reserved in slice 7 for use by Solaris Volume Manager. The remainder of the space on each drive is placed into slice 0. Any existing data on the disks is lost by repartitioning.

After you add a drive to a disk set, you may repartition it as necessary, with the exception that slice 7 is not altered in any way.

The following output from the prtvtoc command shows a disk before it is added to a disk set.

[root@lexicon:apps]$ prtvtoc /dev/rdsk/c1t6d0s0
* /dev/rdsk/c1t6d0s0 partition map
*
* Dimensions:
*     512 bytes/sector
*     133 sectors/track
*      27 tracks/cylinder
*    3591 sectors/cylinder
*    4926 cylinders
*    4924 accessible cylinders
*
* Flags:
*   1: unmountable
*  10: read-only
*
*                          First     Sector    Last
* Partition  Tag  Flags    Sector     Count    Sector  Mount Directory
       0      2    00          0   4111695   4111694
       1      3    01    4111695   1235304   5346998
       2      5    01          0  17682084  17682083
       3      0    00    5346999   4197879   9544877
       4      0    00    9544878   4197879  13742756
       5      0    00   13742757   3939327  17682083

The above output shows that the disk does not contain a slice 7. Therefore, when the disk is added to a disk set, Solaris Volume Manager repartitions the disk. The following output from the prtvtoc command shows the disk after it is added to a disk set.

[root@lexicon:apps]$ prtvtoc /dev/rdsk/c1t6d0s0
* /dev/rdsk/c1t6d0s0 partition map
*
* Dimensions:
*     512 bytes/sector
*     133 sectors/track
*      27 tracks/cylinder
*    3591 sectors/cylinder
*    4926 cylinders
*    4924 accessible cylinders
*
* Flags:
*   1: unmountable
*  10: read-only
*
*                          First     Sector    Last
* Partition  Tag  Flags    Sector     Count    Sector  Mount Directory
       0      0    00      10773  17671311  17682083
       7      0    01          0     10773     10772
[root@lexicon:apps]$ 

The output shows that the disk has been repartitioned to include a slice 7 that starts at cylinder 0 and that has sufficient space for the state database replica. If disks you add to a disk set each have an acceptable slice 7, they are not reformatted.

If you have disk sets that you upgraded from Solstice DiskSuite software, the default state database replica size on those sets is 1034 blocks, not the 8192 block size from Solaris Volume Manager. Also, slice 7 on the disks that were added under Solstice DiskSuite software are correspondingly smaller than slice 7 on disks that were added under Solaris Volume Manager.