Questions related to active file management

Issues and explanations pertaining to active file management.

The following questions are related to active file management (AFM).

How can I change the mode of a fileset?

The mode of an AFM client cache fileset cannot be changed from local-update mode to any other mode; however, it can be changed from read-only to single-writer (and vice versa), and from either read-only or single-writer to local-update.

To change the mode, do the following:
  1. Ensure that fileset status is active and that the gateway is available.
  2. Unmount the file system.
  3. Unlink the fileset.
  4. Run the mmchfileset command to change the mode.
  5. Mount the file system again.
  6. Link the fileset again.

Why are setuid/setgid bits in a single-writer cache reset at home after data is appended?

The setuid/setgid bits in a single-writer cache are reset at home after data is appended to files on which those bits were previously set and synced. This is because over NFS, a write operation to a setuid file resets the setuid bit.

How can I traverse a directory that has not been cached?

On a fileset whose metadata in all sub-directories is not cached, any application that optimizes by assuming that directories contain two fewer sub-directories than their hard link count does not traverse the last subdirectory. One such example is find; on Linux®, a workaround for this is to use find -noleaf to correctly traverse a directory that has not been cached.

What extended attribute size is supported?

For an operating system in the gateway whose Linux kernel version is less than 2.6.32, the NFS max rsize is 32K, so AFM would not support an extended attribute size of more than 32K on that gateway.

What should I do when my file system or fileset is getting full?

The .ptrash directory is present in cache and home. In some cases, where there is a conflict that AFM cannot resolve automatically, the file is moved to .ptrash at cache or home. In cache the .ptrash gets cleaned up when eviction is triggered. At home, it is not cleared automatically. When the administrator is looking to clear some space, the .ptrash should be cleaned up first.