BackBox H4.00 User Manual

Configuration
38 BackBox H4.00 User Manual
Options for BACKUP, BRCOM and TMF
These options should be revised taking into consideration the differences between
physical and virtual tape media. Some options apply to real media but not
necessarily to virtual media For example, the value of the tape feature VERIFYTAPE
can be reconsidered when the data is actually written to a disk file.
Ensure to always use the maximum BLOCKSIZE. Use 52 K in BACKUP and TMFCOM
DUMP FILES commands. The block size of TMF Audit dump must be configured by
TMFCOM. BRCOM uses the maximum 56 K by default.
Avoid using NOUNLOAD
Characteristics of virtual volumes
Size of virtual volumes
The maximum size of virtual volumes is configured by Volume Group. Note that the
allocated size of a virtual volume is limited to the size effectively used for the data,
after compression if applicable, in both Windows file and TSM Data Stores.
This size should be consistent with the media capacity expected by software like
DSM/TC and TMF. For example, very small size such as 5 MB should be avoided; see
Number of volumes below.
If virtual volumes are to be exported to physical media, the amount of uncompressed
data must fit on a single physical media.
Similarly, the content of a physical media must fit in a single virtual volume when
imported.
The maximum volume size must be supported by the Data Store.
In Windows files Data Stores, the maximum volume size plus 10% must fit in a
single disk.
In TSM API Data Stores, the Volume Group configuration allows the split of a single
virtual volume in several TSM objects, allowing very large virtual volume size. See
details in the Volume Group, GUI chapter.
Smaller volumes can reduce the time for a partial restore in a multi volume backup,
when BACKUP was executed with the CATLOGFILES option, or when the user keeps
backup output report and chooses the required volumes in this report for the partial
restore. The benefit is especially important if the Data Store is Windows files with
archive scripting and if the Windows files must be restored on Windows disk before
the virtual volume load can be completed.
Because each volume load introduces a delay, very small virtual volumes will
significantly increase the time to complete a multi-volumes restore operation.
The maximum volume size is usually set from 10 to 50 GB.