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Don Burleson Blog 







Oracle ASM Cluster Filesystem (ACFS) Tips

Oracle11g Release 2 Tips by Burleson Consulting

Question:  What does the AFCS do in Oracle 11gr2 and beyond  Can you give an example of using AFCS?

Answer:  11gr2 introduced the Oracle Automatic Storage Management Cluster File System (Oracle ACFS).  ASM Cluster Filesystem (ACFS) is also named "Unified Storage Management" (UFS) and allows for storing Application File Data , the Oracle Cluster Registry (OCR), the Cluster Voting Disk, and the Oracle Binaries, all within ASM.

ACFS is an extension to Oracle ASM (Automatic Storage Management) that allows customer-specific non-Oracle files to be stored in a cluster file system. While ASM is used mainly for the database, ACFS can now be used to store any kind of non-database files.

The interesting thing is that along with the cluster file system, Oracle has provided the facility of ACFS Snapshots for the first time, and this is exciting news.

This is a read-only, point in time copy of an Oracle ACFS file system, much like the NetApp snapshots we talked about in the earlier section. Each snapshot is space-efficient and up to 63 snapshot views are supported for each file system.

The ACFS snapshots are administered using the acfsutil snap commands, such as acfsutil snap create and acfsutil snap delete.

The Oracle ACFS snapshots can also be administered using Oracle Enterprise Manager. When you log in to the console you will notice that the ASM Home page that manages ASM now has an ASM Cluster File System tab.

ASM Cluster Filesystem (ACFS) in 11gR2

Answer:  (by Lutz Hartmann, Oracle ACE)

Note:  There is a vulnerability exposure RAC on ASM:

"When using RAC, Oracle has announced that the key clusterware files, the OCR and Votedisks, can now be stored in Oracle Automated Storage Management (ASM). 

However, research by our BC expert DBA's indicate that it may well be premature to use this feature.

According to Oracle's documentation, the 11gR2 Clusterware Administration and Deployment Guide (chapter 2) , if a single node is lost, then the entire cluster may go down, if that node happens to be the master node."

 The rumors are becoming reality. Although this book is in the final production phase already I want to take this chance to give a brief outlook to the upcoming features for Oracle brand new release 11gR2. All the information in this chapter is based on the documentation for the beta release of 11gR2.

I was not able to test and verify all these features so there might be some unexpected surprises. My primary intention was to give a last minute overview of what is coming up in storage administration in 11gR2.

As I had already mentioned in my ASM chapter Oracle Corporation has been working with enormous effort to create a POSIX?X OPEN based file system for ASM storage. There were talks about it since more than one year.

This feature is called ACFS and will be available in 11gR2 for LINUX and UNIXs. For Windows there will also be a similar solution available.

ACFS will work with Single Instance Installations as well as Clusters. It is strongly integrated with the Oracle Clusterware. Supported protocols for NAS are NFS and CIFS.

This new feature is also named Unified Storage Management and allows for storing the following data in ASM:


-          Application File Data

-          Oracle Cluster Registry (OCR)

-          Cluster Voting Disk

-          Oracle Binaries

Now we will have all the trace files, alert.log, reports and so forth in ASM which makes ASM a complete storage management system finally for both database and non-database files and completely eliminates the need for any 3rd. party cluster file systems.

ACFS uses a journaling mechanism and uses endian independent metadata to support large files and file systems to an extent up to exabytes.  A special metadata log structure is maintained for integrity checks and fast recovery through a metadata transaction engine.

File systems in ASM can dynamically be expended and contracted with no downtime. High availability is fully supported through mirroring and striping capabilities for all files now with ASM!





If you like Oracle tuning, you may enjoy my new book "Oracle Tuning: The Definitive Reference", over 900 pages of BC's favorite tuning tips & scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.



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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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