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 Oracle RAC Architecture

 

 

  1. Where are the clusterware files stored on a RAC environment?
  2. Where are the database software files stored on a RAC environment?
  3. What kind of storage we can use for the shared clusterware files?
  4. What kind of storage we can use for the RAC database storage?
  5. What is a CFS?
  6. What is an OCFS2?


    7. Which files can be placed on an Oracle Cluster File System?
    8. Do you know another Cluster Vendor?
    9. How is possible to install a RAC if we don’t have a CFS?
  10. What is a raw device?
  11. What is a raw partition?
  12. When to use CFS over raw?
  13. When to use raw over CFS?
  14. What CRS is?

 

 

1. Where are the clusterware files stored on a RAC environment?

 

The clusterware is installed on each node (on an Oracle Home) and on the shared disks (the voting disks and the CSR file)

 

 

2. Where are the database software files stored on a RAC environment?

 

The base software is installed on each node of the cluster and the database storage on the shared disks. 

 

 

3. What kind of storage we can use for the shared clusterware files?

 

- OCFS (Release 1 or 2) 
- raw devices 
- third party cluster filesystem such as GPFS or Veritas 

 

 

4. What kind of storage we can use for the RAC database storage?

 

- OCFS (Release 1 or 2) 
- ASM 
- raw devices 
- third party cluster filesystem such as GPFS or Veritas

 

 

5. What is a CFS?

 

A cluster File System (CFS) is a file system that may be accessed (read and write) by all members in a cluster at the same time. This implies that all members of a cluster have the same view. 

 

 

6. What is an OCFS2?

 

The OCFS2 is the Oracle (version 2) Cluster File System which can be used for the Oracle Real Application Cluster. 

 

 

7. Which files can be placed on an Oracle Cluster File System?

 

- Oracle Software installation (Windows only)
- Oracle files (controlfiles, datafiles, redologs, files described by the bfile datatype)
- Shared configuration files (spfile)
- OCR and voting disk
- Files created by Oracle during runtime 

 

Note: There are some platform specific limitations. 

 

 

8. Do you know another Cluster Vendor?

 

HP Tru64 Unix, Veritas, Microsoft 

 

 

9. How is possible to install a RAC if we don’t have a CFS?

 

This is possible by using a raw device. 

 

 

10. What is a raw device?

 

A raw device is a disk drive that does not yet have a file system set up. Raw devices are used for Real Application Clusters since they enable the sharing of disks. 

 

 

11. What is a raw partition?

 

A raw partition is a portion of a physical disk that is accessed at the lowest possible level. A raw partition is created when an extended partition is created and logical partitions are assigned to it without any formatting. Once formatting is complete, it is called cooked partition.

 

 

12. When to use CFS over raw?

 

A CFS offers:
- Simpler management
- Use of Oracle Managed Files with RAC
- Single Oracle Software installation
- Autoextend enabled on Oracle datafiles
- Uniform accessibility to archive logs in case of physical node failure
- With Oracle_Home on CFS, when you apply Oracle patches CFS guarantees that the updated Oracle_Home is visible to all nodes in the cluster.

 

Note: This option is very dependent on the availability of a CFS on your platform.

 

13. When to use raw over CFS?

 

- Always when CFS is not available or not supported by Oracle.
- The performance is very, very important: Raw devices offer best performance without any intermediate layer between Oracle and the disk.
Note: Autoextend fails on raw devices if the space is exhausted. However the space could be added online if needed.

 

 

14. What CRS is?

 

Oracle RAC 10g Release 1 introduced Oracle Cluster Ready Services (CRS), a platform-independent set of system services for cluster environments. In Release 2, Oracle has renamed this product to Oracle Clusterware.

 

 

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