HP NonStop G-Series - Manual (Page 55)

Configuring and Managing SMF Processes
HP NonStop Storage Management Foundation User's Guide—523562-008
3-5
Considerations for Virtual Disk Processes
include the VDP name, the location of its catalogs, its primary and backup CPUs, and
the amount of VDP cache to be configured.
Naming Virtual Disk Processes
When migrating existing data to SMF, users generally choose virtual disk names to
preserve existing disk names by replacing physical disk names with VDP names. If you
use the SMCONVRT utility, it will do this automatically. For large configurations where
you do not need to preserve existing disk names, it is often useful to encode the pool
or CPU identity in the VDP name. For example, you could use the name $V
xxnnn ,
where xx is the pool or CPU number, and nnn is a sequential number within that pool
or CPU. For virtual disks created to perform generic functions, use a descriptive name
such as $TEMP or $WORK.
While it is possible to create 7-character virtual disk process names, HP recommends
that VDP names be limited to 6 characters, as some SQL network operations limit a
volume name to "$" followed by no more than 6 characters.
Virtual Disk Catalog Placement
Virtual disk catalogs must be located on a mirrored, audited disk that is a member of
any storage pool on the system. Unlike the pool process catalog, virtual disk catalogs
are heavily used because they are accessed at every CREATE, OPEN, and other file
related request. They can also become large because they contain an entry for every
file created on the virtual disk. For these reasons, it is best to spread the virtual disk
catalogs on multiple disks in different CPUs, rather than concentrating them on a single
disk.
While a virtual disk catalog can be created in any pool, it might make sense to locate
the catalog in the pool to which the virtual disk belongs. This accomplishes two goals.
First, it spreads the virtual disk catalogs so the load is not concentrated on one disk or
in one CPU. Second, it limits the effect of a pool outage due to a problem such as a
physical disk failure. Should a pool become inaccessible, the virtual disks of other
pools will not be affected.
To maximize virtual disk performance, locate the catalog on a disk whose primary CPU
is the same as the virtual disk process whenever possible. This strategy results in
faster communication between the virtual disk process and DP2 when accessing and
updating the catalog.
The virtual disk catalog actually consists of multiple files, including the Audited Name
Table (ANT) and the Pending Operations Table (PENDOPS). The location of these two
tables can be specified separately when the virtual disk is configured. However, HP
does not recommend this method as there are no clear benefits from splitting the ANT
and PENDOPS, and it complicates the configuration.