Creating a multiterabyte UFS snapshot is identical to creating a snapshot for a smaller UFS file system. The only difference is that multiple backing store files are created for each 512 GB of file system space.
Keep the following key points in mind when creating a snapshot for a file system that is larger than 512 GB:
Multiple backing store files are created.
If you specify a backing store file name when the snapshot is created, then the subsequent backing store file names will be interated based on the file name that you specify. The subsequent backing-store files will have the same name, but with the suffixes .2, .3, and so on.
If you only specify a backing store file destination (or directory) and not a backing store file name, then multiple backing store file names will be created and iterated with the suffixes .2, .3, and so on.
The fssnap -i command only reports the first backing store file name even if multiple backing store files have been created. However, the reported backing-store length is the combined sizes of all the backing store files for the snapshot.
Backing-store files are sparse files. The logical size of a sparse file, as reported by the ls command, is not the same as the amount of space that has been allocated to the sparse file, as reported by the du command.
After you have backed up the snapshot or you would just like to remove the snapshot, you will have to remove the backing store files manually if you did not use the unlink option when the snapshot was created.
For an example of creating a snapshot for a file system that is larger than 512 GB, see Example 25–2.
For more information, see fssnap_ufs(1M).