vxfs mount option "delaylog" definition please

[CITEC HP TEAM]

The mount_vxfs man page says that it approximates the older Unix system behaviour. Some white papers I've read say that it increases performnce at the cost of a possible data loss in the event of a system crash, without saying what sort of data.

We are setting up a system under HP-UX 11.11, with Online JFS. It will have multiple Oracle databases and we would like to tune them to perform as well as possible.

I've read 5 or so white papers on the subject and most recommend using delaylog, along with some other options. They do not go in to how the option works however. I can't find anything by searching the web either.

The mount_vxfs man page definition says that some metadata writes are delayed in being written to the intent log. I can live with things like timestamps, chmod, chown being delayed and possibly lost but an inode update resulting from a file extension is another matter. This could cause some real problems for Oracle.

Can someone please point me to where I can find what this option does, so I can understand the risks?

The alternative is to use "log", but this has a performance penalty that I would rather avoid.

[Paul_481]

Hi,

From the man pages of mount_vxfs

"In delaylog mode, some system calls return before the intent log is written. This improves the performance of the system, but some changes are not guaranteed until a short time later when the intent log is written.

This mode approximates traditional UNIX system guarantees for correctness in case of system failures."

Regards,
Paul

[Paul_481]

Oops, didnt see your question. My bad.

[CITEC HP TEAM]

You got me all excited too Paul. I thought I had an answer.