hpux filesystem IO and raw IO

[sagarwal]

I am experiencing that hpux disk driver handles
raw buffer different than file system buffer(vxfs)at blk layer,but i dont see any document or info talking about it.
i see this intresting comments in buf.h ,but could not find any more info.would appreciate if somebody can put more light on these/any doc which can explain these.

/* the following fields are added for third party file systems to use.
* See "HP-UX Kernel Changes for VxFS External Reference Specification"
* section 7 for details.
*/
struct buf *b_nextchain; /* VXFS or NFS */
void *b_private; /* file system private buf info */
int (*b_writestrat) __((struct buf *)); /* this file system has its own
strategy routine for bwrite()
and asyncpageio() */

[Steven E. Protter]

Hi sagarwal,

Kind of depends on the app.

A. Clay Stephenson did a study on Oracle.

With 11i there was viturally no performance bump going with or without raw disk.

Other things being equal.

some issues requires testing, not a whitepaper to be resolved.

SEP

[sagarwal]

thanks steven,
i am not asking this questin in context of oracle application.
i am writing a blk layer filter driver ,which can keep track of changes happening at blklevel.
it works fine on raw devices/raw applications but dont get callback when IO coming from filesystem .

regards
shri