Open System Services Management and Operations Guide (G06.25+, H06.03+)

Managing Filesets
Open System Services Management and Operations Guide—527191-002
5-15
Changing the Operating Parameters of a Fileset
Changing Fileset Buffering
The value used for the BUFFERED option can have a dramatic effect on application
performance when there are a lot of calls to OSS file system functions that involve
pathname resolution (creat(), unlink(), rename(), chmod(), chown(),
mkdir(), and so on). The possible values of the BUFFERED option are, in order of
increasing buffer usage:
NONE
LOG
CREATE
Using the Value NONE
An OSS name server writes a record in the PXLOG file as part of each pathname
resolution operation. When both processes of a OSS name server process pair
involved in the resolution fail, recovering from a partially completed operation is fast
because it is based on the PXLOG file entry.
This option is the most costly at run time but provides the fastest recovery from
complete OSS name server failure.
Using the Value LOG
An OSS name server does not write PXLOG records; it checkpoints these records to
its backup process. The backup process of an OSS name server keeps these records
in its memory and uses them to recover partially completed operations in the event of a
failure of an OSS name server primary process. If total failure of an OSS name server
occurs, FSCK is automatically run against the fileset during the fileset remounting
operation.
This option provides better run-time performance at the expense of slower recovery in
the event of complete OSS name server failure. You can control the relative likelihood
of needing fileset repair, and therefore the relative speed of recovery, by adjusting the
MAXDIRTYINODETIME attribute for the fileset.
Using the Value CREATE
The OSS name server does not write PXLOG records but rather checkpoints these
records to its backup process. The backup process keeps these records in its memory
and uses them to recover partially completed operations in the event of a failure of the
OSS name server primary process. If total failure of the OSS name server occurs,
FSCK is automatically run against the fileset during the fileset remounting operation.
The disk process does not write new file labels immediately but rather defers these
label writes until it has nothing else to do.
This option provides the best run-time performance but limits the fileset to one disk
volume and has the potential for lost files in the event of a double-disk process failure.
See Creating a Unique Fileset on page 5-1 for additional considerations when you use
BUFFERED CREATE.