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Using "Unbuffered" (Direct I/O) with RAC + SFRAC

kkhayer
Level 2

Veritas Storage Foundation for Oracle RAC 5.1
Oracle RAC 10.2.0.5
Currently, MountOpt="mincache=direct" is not set in main.cf.
My questions here are:
- Would it make a difference in write performance if the above option was set (for file systems housing datafiles, redo, and archived redo logs)?- Are there any restrictions/known bugs to avoid setting such parameter?
- There is no reference to setting this option when RAC+SFRAC are integrated together. Oracle Support have a few notes that indicate you will see improvements setting the MountOpt parameter. Please see the following notes:
- Performance impact of file system when mounted as Buffered and Unbuffered option (Doc ID 151719.1).
- Poor Performance Writing Blobs (Doc ID 393780.1).
- Using VRTS file system on top of Sun Cluster Global file system (Doc ID 219368.1).
 


 

1 ACCEPTED SOLUTION

Accepted Solutions

ScottK
Level 5
Employee

Since you are using SFRAC & Oracle RAC, I/O should be going through the ODM interface (assuming everything is properly configured).

ODM is an API between Oracle and the Veritas File System. I/O going through ODM is not buffered, nor locked by VxFS. This allows Oracle to manage both memory and locking, which increases performance in most cases. The mincache setting does not affect ODM, but I/O going through normal read/write calls.

If you have files outside of Oracle, those are the ones that would benefit.

View solution in original post

3 REPLIES 3

ScottK
Level 5
Employee

Since you are using SFRAC & Oracle RAC, I/O should be going through the ODM interface (assuming everything is properly configured).

ODM is an API between Oracle and the Veritas File System. I/O going through ODM is not buffered, nor locked by VxFS. This allows Oracle to manage both memory and locking, which increases performance in most cases. The mincache setting does not affect ODM, but I/O going through normal read/write calls.

If you have files outside of Oracle, those are the ones that would benefit.

View solution in original post

kkhayer
Level 2

We do have ODM in place:

From the install doc,”sfrac_install_so.pdf”  page 231. I see that MountOpt="mincache=direct" is set for ocr/vote. No ODM here?

przemol
Level 4

Regarding ODM: you can use ODM by setting link from libodm* file to Veritas libodm* file:

[ standard setting ]

libodm9.so -> libodmd9.so

 

[ODM from Veritas ]

libodm9.so -> /opt/VRTSodm/lib/sparcv9/libodm.so

 

And I confirm that ODM is a big boost - especially in write intensive environments.