set mincache=direct in an FS

[silusan]

I want /dev/vg/lv FS to have mincache=direct option.

How do I do that? do i need to unmount the FS and do that?

guest:/ # fstyp -v /dev/vg/lv
vxfs
version: 7
f_bsize: 8192
f_frsize: 1024
f_blocks: 134807552
f_bfree: 109570000
f_bavail: 102721875
f_files: 27393044
f_ffree: 27392500
f_favail: 27392500
f_fsid: 1073872897
f_basetype: vxfs
f_namemax: 254
f_magic: a501fcf5
f_featurebits: 0
f_flag: 16
f_fsindex: 9
f_size: 134807552
guest:/ #

/etc/fstab
/dev/vg/lv /mount/point vxfs defaults 0 2.

thanks

[Ken Grabowski]

I believe the mincache=direct is a SUN mount option that turns off the buffering and logging of O_SYNC or O_DSYNC.  If your trying to reduce FS overhead and delay, for a lot of small data writes like a database log, you can try adding the mount options; convosync=direct or  convosync=unbuffered, and nodatainlog. You may also see a benefit by creating the vxfs file system with a bsize that's friendly to your writes. I have see significant performance benefits with database log file systems by using mkfs bsize=2048 and mount nodatainlog.

Before use any of these options make sure you have a GOOD performance test defined, a GOOD baseline test, and test every change.  Setting the wrong options for buffers and logs on a vxfs file system can bring your FS performance down to a crawl.

[Dave Olker]

Check out the man page for mount_vxfs for available VxFS mount options and their usage.

Dave