Air Cleaner User Manual

v If no physical volumes are selected for the logical volume: a maximum
value spreads the logical volume across either all of the disks in the
volume group or the value in the Maximum PVs field, whichever is less.
A minimum value uses the first disk in the volume group unless it fills,
in which case the next disk in the volume group is used for the
remainder.
v If you select physical volumes for this logical volume, a maximum value
spreads the logical volume across all of the disks selected for the logical
volume, not to exceed the value of the Maximum PVs field. A minimum
value uses the first disk in the list should be used unless it fills, in which
case the next disk in the list is used.
v If only one disk has been selected for the logical volume or volume
group, this policy has no affect.
v If the Stripe size is set to any value other than zero (0), this policy has
no effect.
Stripe Size
The current stripe size (in K-bytes) or “0” if the logical volume is not
striped. Striping a logical volume means that data is inter-dispersed
throughout the specific physical volumes in blocks of data indicated by the
stripe size. Striping usually benefits random I/O performance, but having
a logical volume spread over more than on physical volume causes the
entire logical volume to be unreadable if any of the disks containing a part
of the logical volume becomes unavailable.
For a logical volume to be striped, you must first assign two or more
physical volumes to this logical volume, and the number of logical
partitions (LPs) must be a multiple of the number of disks selected. You
must enter the stripe size in K-bytes (1024 byte blocks). Valid values are 0,
4, 16, 32, 64 or 128. Setting the value to “0” indicates the logical volume
will not be striped.
You cannot change this field if you are installing the system from a power
backup, if the logical volume is to be created using a partition map (Use
PP map? field), or if the number of Copies is greater than 1.
Use PP map?
Indicates whether or not to preserve physical partition mapping. This
value is set to “no” by default, or to “yes” if you selected to preserve
physical partition mapping when the backup was created.
Select “y” to retain the exact prior physical partition placement of the
logical volume as it was placed on the original system. Creating a logical
volume using the partition map is typically performed only if the logical
volume was originally created using a partition map. If the logical volume
was not originally created using a map, doing so now often retain the
partition fragmentation that exists after logical volumes are periodically
increased in size. This would usually negatively impact I/O performance
to this logical volume.
When you use a map to create a logical volume, the prior physical
volumes must still exist and be of the same size. You cannot change the
size, number of copies, striping, or physical volumes for a mapped logical
volume. Also, the Intra-policy and Inter-policy are ignored.
Select “n” to not retain the prior physical partition map. In this case, the
partitions in the logical volume are created contiguously, resulting, in most
cases, in increased I/O performance. The logical volume will, however,
11-14 IBM Tivoli Storage Manager for System Backup and Recovery: Installation and User’s Guide