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Figure 5. Basic HPSS Metadata & Filesystem Allocation
On the left hand side of the diagram, the raw physical volumes are shown attached to the disk array
controller. The configuration of the disks by the controller and its software should be divided into
three separate LUNs: 1) HPSS Filesystems and DB2 Backups, 2) DB2 Logs, 3) and the DB2 Tables.
One disk may be kept as as a "hot spare" in the event that one of the other disks fails. This allows the
system to automatically replace the failed media and rebuild the data without immediate intervention
from an operator or administrator. Recommended configurations for the LUNs is to use RAID 5,
which is good for small, random data access, for the first and third LUN. For the LUN associated
with DB2 Logs, it is suggested that RAID 1 (Mirroring) be used since these logs are typically very
large and accessed sequentially by the system. Once defined, these LUNs are assigned to the core
server host via the LVM (AIX) into a Volume Group or by the operating system (Linux) into a hard
drive identifier. The last step is to allocate individual filesystems and logical
volumes(AIX)/partitions(Linux) as defined on the right-hand side of the diagram.
HPSS requires the use of DB2 log mirroring. This protects the active DB2 log from possible loss due
to the primary metadata disk array failure or other unavailability. To safe guard the DB2 log,
separate disk/controller components are required for the LUNs providing storage for the filesystem
where the log is written as well as where the archived copies of the logs are stored before being
backed up to tape media. It is imperative that the components be totally separate from the primary
metadata disk array (i.e. different disks, different controllers, different path such as the FC
connections) to provide protection against failures. Specific resource assignment for the the
HPSS Installation Guide July 2008
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