Using Oracle ACFS for a General Purpose File System

By Scott Jesse, Bill Burton, Bryan Vongray on September 27, 2013


You may have worked out that an Automatic Storage Manager (ASM) Cluster File System (ACFS)for shared Oracle home use is just an ACFS under CRS control—so what about an ACFS for general purposes?

Once you create an ACFS file system with mkfs, it can be used in exactly the same way as any POSIX-compliant file system. You could say that it needs no further action or management other than to mount it and go. The only slight problem with that, however, is when it comes to mounting it automatically at boot time. The file system requires ASM to be up, the underlying disk groups to be mounted, and the ADVM drivers to be loaded, so we need to have something that ensures that all this is true before the mount occurs. The ACFS mount registry is the tool for this; it is managed using the acfsutil command.

The general purpose ACFS can be used for anything, but it’s ideal for the following:

  • Diagnostic destination If you’ve used versions 11.1 and 11.2, you may know this feature as the Automatic Diagnostic Repository (ADR), but beginning in 10.2 RDBMSs, you can as easily mount your ORACLE_HOME/admin directory or wherever your bdump, udump, and cdump directories exist. Not only is it a good idea to have all the instance’s trace files in a common store to be viewed from a single node in the cluster, but having a separate file system for trace files can help with file space management. Although the GI home cannot be on the ACFS, the ASM diagnostic destination can be. Be careful that you don’t fill the file system, however, because that can cause clusterwide problems.
  • External database files and directories Having a shared file system for BFile data types and external directories ensures that the files are available no matter what instance you are running on.
  • Applications Many applications require that common store be used for documents and reports. If the application lives on a middle tier, either GI must be installed on those cluster nodes or exiting ACFSs can be exported using NFS and mounted on those mid-tier servers.

ACFS mount registry

The ACFS mount registry can be compared to the /etc/fstab on Linux because it stores information about file systems that require mounting at boot time. One major difference between the registry and fstab is that the registry manages the mounts across the cluster and communicates with CRS to ensure that the required resources are started before mounting. The mount registry is managed using the acfsutil command, and all general purpose file systems should be registered with the mount registry. You must not, however, register CRS-managed ACFSs with the mount registry; it is one or the other, but never both.

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