HP 3000 Manuals HP 3000 Manuals
Volume Management Planning MPE XL volume management keeps as much data available as possible. The System Manager can partition data to minimize the loss of access if a volume goes down. The three levels of partitioning are: * Volume Set Restriction * Volume Class Restriction * Volume Restriction Volume Set Restriction The default volume restriction is the volume set of the group where the file resides. File extents are placed on any volume within the volume set. This option offers the least protection for file access if a volume goes down. If the master volume of the set goes down, access to the entire volume set is denied for disk space allocation.
NOTE The more specific the restrictions, the more likely that data will not be lost in the unlikely event of a device or media failure. However, there may be a performance penalty for being more restrictive. Use this feature wisely.
Volume Class Restriction Volume class is the next level of restriction. With the exception of the volume class "DISC," volume class restriction must be specified at file creation time. A file is placed only on volumes within a volume class. If the volume class is a small subset of the volume set, it is less likely to prevent access to data if a disk goes down. Volume Restriction Volume restriction is the most effective level of protection. Volume restriction must be specified at file creation time. The file extents are placed only on one volume. Nonsystem Volume Set Restriction Nonsystem volume sets can serve as another type of restriction. It allows the volume class and volume restrictions. Multiple volume sets with few members provide the advantages of volume sets that can be moved to other systems and backed up separately. System managers are encouraged to have most of their accounting structure on nonsystem volume sets for higher data availability. There is little difference in the time to access nonsystem versus system volumes sets.