11gR2 – ASM redundancy levels.


In 11gR2 ASM diskgroups are used 1) by Grid infrastructure for the OCR, Voting disk and the ASMspfile. 2) by the database for DATA and FRA.

ASM redundancy levels, can be a bit misleading in Oracle 11gR2 compared to 10gR2.   They are called the same, Normal redundancy, High Redundancy and External Redundancy.  However, depending on what area of the 11gR2 configuration this will be used, the number of disks required to configure are not the same.  DBA’s seldom are able to take the difference into consideration when requesting disks /LUN’s from the storage administrators and are taken by surprise during installation.

Grid Infrastructure:  When configuring diskgroups for the OCR file, voting disk and ASMspfile, Normal redundancy requires 3 disks/LUNS to be part of the diskgroup.  High redundancy requires 5 disks/LUNS to be part of the diskgroup.  External redundancy requires just one disk/LUN to be part of the diskgroup. The below screen output shows the error message when only one disk/LUN is selected for the GRID diskgroup.


Database: When configuring diskgroups for DATA and FRA, normal redundancy requires 2 disks/LUNS to be part of the diskgroup.  High redundancy requires 3 disks/LUNs or failure groups to be part of the diskgroup.  External redundancy requires just one disk/LUNs or failure groups to be part of the diskgroup


More about configuring OCR and voting disks in the next post.


Back from OOW 2007

Just returned from OOW’2007. As usual this is one of the events that tend to be pretty hectic with several sessions and events that get scheduled in parallel and you end up confused on which one would be better to pick. Though several times, several of us think that OOW is Oracle’s show case to show off what is coming or some kind of marketing talk. Over the past couple of years, I have noticed that this is not completely true. There are presentations that contains product and new release overview, if you carefully select the presentation titles, you can get some good technical presentation.

Some of the good technical sessions I had attended were the performance tuning for data warehouses, performance tuning roundtable, performance tuning RAC and several of the IOUG and SIG events.

OOW started on Sunday with various SIGs presenting in their respective areas. I had presented a topic on Parallel queries in Oracle RAC for the RAC-SIG on Sunday.


At OOW, we also released a book on Oracle Automatic Storage Management (ASM) published by Oracle Press. This book is a combined effort of Nitin, Rich Long and myself. I am happy that the contents are pretty well covered from the basics of storage management to some internals and also to topics such as how to change the paradigm of the current of storage management implementation.


This week had another great importance, a dream had come true, and a dream I had been working on for several years had become a reality. While every country had an Oracle Users Group that provided knowledge and information sharing to Oracle users, one such group was long past due in India. I had been working on getting one started over the past several years. I am happy to say we officially went live with this group. Those interested should check the user group website at www.aioug.org