HP-UX 11i Version 2 Release Notes (October 2003)

Disk and File Management
Swap Space Adjustment for Large Memory-Mapped Files
Chapter 5
116
Impact
The same SLVM functionality that is currently available to you has been extended to
larger clusters.
Compatibility
These changes are fully backward-compatible.
Performance
For existing configurations, these changes will not have any effect on performance.
Documentation
Supported configurations are documented in MC/ServiceGuard Version A.11.15.00
Release Notes, available at http://www.docs.hp.com.
Obsolescence
Not applicable.
Swap Space Adjustment for Large Memory-Mapped
Files
With HP-UX 11i v2, VxFs enables the creation of file system sizes up to 4 TB. Files can
be a maximum of 2 TB. (See “VERITAS File System (VxFS) 3.5” on page 117.) Because of
this, you should be aware of adjustments that may be necessary when you configure
system swap space.
When you configure the amount of swap space for the system, an adjustment should be
made if necessary to provide for large, memory-mapped files.
As the size of a memory-mapped file increases, the swap consumption for storing the
related metadata will also increase. So, if the system will have many large
memory-mapped files at runtime, then the swap on the system also must increase. For
example, a 1 TB file will probably require about 4 GB of swap space for storing
metadata. So for 10 such files, about 40 GB of swap space will be needed just for
metadata.