When invoked with the -n option, vxupgrade upgrades the disk layout to the specified version. When invoked without the the -n option, vxfs prints the disk layout version number of the file system.
vxupgrade makes use of a lock file (lost+found/.fsadm) on the file system to ensure that only one instance of vxupgrade is running at any time. vxupgrade and fsadm cannot be run simultaneously, so the lock file also ensures that vxupgrade is not run while a file system reorganization is in progress. When vxupgrade is invoked for an upgrade, it opens the lock file in the root of the file system specified by mount_point. If the file doesn't exist, it is created. The fcntl(S) system call is used to obtain a write lock on the file. If the write lock fails, vxupgrade will assume that another vxupgrade or an fsadm is running and will fail (see fsadm(ADM).
Once a file system has been upgraded to disk layout Version 2, it is no longer mountable with releases of VxFS prior to VxFS 2.0.
File systems cannot be downgraded.
To upgrade a disk layout Version 1 file system with n * 1024 inodes (total of both allocated and free inodes) to disk layout Version 2, a worst-case minimum value is at least n * 896 bytes + 371 Kbytes, in extents of 8 Kbytes or larger. Free extents of larger than 8 Kbytes may be required, and n must be rounded up to an integral value, so this is only a lower bound on the worst case-minimum. Since this is the worst-case minimum, it may be possible to upgrade with less free space available.
To upgrade a disk layout Version 2 file system with n * 1024 inodes (allocated only) and m * 32768 blocks to disk layout Version 4, the worst-case minimum value is at least n * 2432 bytes + m * 8220 bytes + 115 Kbytes, in extents of 8 Kbytes or larger. Free extents of larger than 8 Kbytes may be required, so this is only a lower bound on the worst-case minimum required. Since this is the worst-case minimum, it may be possible to upgrade with less free space available. After the upgrade to disk layout Version 4 is completed, all of this free space, plus some additional free space, will be reclaimed.
A request to upgrade a Version 1 disk layout to Version 4 will first upgrade to Version 2 and then to Version 4. The upgrade may fail due to a lack of free space at each step.