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VxFS and FCL upgrade and downgrade

VxFS 4.1 supported only FCL Version 3. VxFS 5.0 supports both FCL Version 3 and 4, with Version 4 as the default. When a system is upgraded from VxFS 4.1 to VxFS 5.0, and the file system has FCL switched on, the existing Version 3 FCL files remains as is. VxFS 5.0 continues tracking file system changes in the Version 3 FCL exactly as it was done by VxFS 4.1.

A VxFS 4.1 application that directly accesses the FCL file using the read(2) system call can still continue to work in 5.0 provided that the FCL file is Version 3. However, you must develop any new applications using the API. The API has support for both FCL Versions 3 and 4.

If a new application uses the newly added record types in VxFS 5.0 such as file opens or access information, etc., the FCL needs to be at Version 4.

If you are running applications that still read FCL Version 3 directly, you cannot upgrade to FCL Version 4 until those applications are rewritten to use the new API. The API can interpret both Version 3 and Version 4, so applications can be upgraded to use the API while Version 3 is still in effect.

Converting FCL Version 3 files to Version 4

The following provides the path for moving from FCL Version 3 to 4:

1. Switch off the FCL.

   # fcladm off mntpt

2. Remove the existing FCL file.

   # fcladm rm mntpt

3. Re-activate with the required version.

   # fcladm [-oversion=4] on mntpt

Downgrading VxFS versions

During data center operations, a VxFS file system might need to be migrated from a host running a newer version of VxFS to a host running an older version (for example, from VxFS 5.0 to VxFS 4.1). Such a migration might occur for offhost processing. If the FCL file created under VxFS 5.0 is FCL Version 3, it can continue to be used (as is) under VxFS 4.1. However, if the FCL file is Version 4, it must first be removed using fcladm rm and then reactivated as FCL Version 3 before it can be used under VxFS 4.1.

Otherwise, if you attempt to open a VxFS 5.0 Version 4 FCL file under VxFS 4.1, the operation will fail.

  Note   It is the responsibility of the off-host application to invoke a sync on the node containing the FCL, before saving and shipping an image of the FCL. The sync ensures that the FCL is brought to a stable state and guarantees that all file writes or opens after the sync, produce an FCL record.