Troubleshooting ACFS-07981: Metadata Validation Errors

Introduction

The ACFS-07981 error indicates that an attempt to run an online file system check (online fsck) on an ACFS file system has failed. The cause is that online fsck couldn't copy the global ACFS metadata to its Copy-On-Write (COW) file. This problem is almost always tied to an underlying metadata validation error, which is why the error message points you to the Oracle Kernel Services (OKS) persistent logs.

This guide will walk you through the necessary steps to diagnose and resolve the issue by examining the logs and deciding on the appropriate corrective action.

---

Understanding the Error

When you run an online file system check on an ACFS filesystem using the acfsutil fsck online command, it attempts to validate the filesystem's metadata without taking it offline. To do this, it first makes a copy of the metadata in a special "Copy-On-Write" file. The ACFS-07981 error signals that this initial copy operation failed, often because there's an inconsistency in the existing metadata that prevents it from being copied.

The key to resolving this is to find the specific metadata validation errors in the OKS persistent logs. These logs provide the low-level details of what's wrong with the filesystem's structure.

---

Step-by-Step Resolution

Follow these steps to find and address the root cause of the ACFS-07981 error.

Step 1: Locate and Examine the OKS Persistent Logs

The first and most critical step is to find the logs that the error message is referring to. These are the Oracle Kernel Services (OKS) persistent logs.

1. Locate the log files:

   The OKS persistent logs are typically located within the Oracle Grid Infrastructure home, under a path similar to $GRID_HOME/log/<hostname>/oks/acfs.log*. You'll want to check the most recent log files.

   Bash

   # Example command to find logs
   $ ls -l $GRID_HOME/log/$(hostname -s)/oks/
   

   You'll likely see files like acfs.log.0, acfs.log.1, and so on.

2. Search the logs for errors:

   Use grep to search for relevant error messages within the log files. Look for keywords like "metadata validation", "inconsistency", or specific error codes.

   Bash

   $ grep "metadata validation" $GRID_HOME/log/$(hostname -s)/oks/acfs.log.0
   

   The output of this command will provide the specific details of the metadata inconsistency. For example, it might mention a corrupted superblock or a problem with a specific inode.

---

Step 2: Decide on the Corrective Action

Based on whether you find metadata validation errors in the logs, your next steps will differ.

• Scenario A: Metadata validation errors ARE found.

  If the logs confirm metadata inconsistencies, it is highly likely that online fsck will not be able to fix the issue. The only way to repair the filesystem is to perform an offline fsck. This requires unmounting the ACFS filesystem, which will cause downtime for any applications using it.

  Action:

  1. Unmount the filesystem:

     Bash

     # umount /your/acfs/mountpoint
     

  2. Run an offline fsck:

     Use the acfsutil fsck command without the online flag to repair the filesystem.

     Bash

     # acfsutil fsck /your/acfs/mountpoint -a
     

     The -a flag tells the utility to automatically attempt to fix any errors it finds.

  3. Remount the filesystem:

     After the fsck completes, remount the filesystem.

     Bash

     # mount -t acfs /dev/asm/yourvolume-123 /your/acfs/mountpoint
     

• Scenario B: Metadata validation errors are NOT found.

  If the OKS logs don't show any metadata validation errors, the problem might be a different kind of runtime issue. The logs may point to a communication error, a low memory condition, or another problem.

  Action:

  1. Resolve the new error:

     Examine the other errors found in the logs and address them. This may involve fixing network connectivity issues, increasing available memory, or resolving other Clusterware-related problems.

  2. Retry the online fsck:

     Once the other issues are resolved, try running the online fsck command again.

     Bash

     $ acfsutil fsck online /your/acfs/mountpoint
     

---

Video Resources

• Understanding Oracle ASM and ACFS Architecture: A foundational video that explains how ACFS, ASM, and the Oracle Kernel Services (OKS) interact. This knowledge is essential for understanding why and where these errors occur.

• Oracle ACFS Online FS Check: A demonstration of the online fsck process and a discussion of its benefits and limitations. This helps visualize the process that is failing with the ACFS-07981 error.

---

Conclusion

The ACFS-07981 error is a clear signal that something is wrong with your ACFS filesystem's metadata. By following the recommended action to meticulously examine the OKS persistent logs, you can determine if the problem is a genuine metadata corruption or a different issue. If you find metadata errors, an offline fsck is the definitive solution, while other errors may be resolved by addressing the specific problem in the logs before retrying the online check.