A little more info on why 'rwm' takes so long. This is not 100% perfectly technically accurate but close enough:

empeg is using the ext2 filesystem for its partitions. The equivalent of the FAT under DOS/Windows is stored on ext2 (and other UNIX filesystems) in multiple locations on the drive. The larger the filesystem, the more locations that superblock backup is kept. That way if one of them gets corrupted, there are multiple copies to refer to instead of just one backup as is the case with FAT. Since even a small empeg still has nearly a 6GB filesystem as its data partition, thats a LOT of copies of the superblock scattered across the disk. One of the pieces of information contained in each superblock backup is the "Dirty bit" mentioned a little earlier. That is a bit that is set any time the partition is mounted read-write and cleared anytime the partition is unmounted. (when you "rom" you are unmounting the partition first, then remounting it read-only which does not affect the "Dirty bit.") A reason "rwm" takes so long is because it's having to update a lot of copies of that "dirty bit" in all the superblocks stored across the filesystem. Another thing that mounting the ext2 filesystem "rwm" does is just do a quick "sanity check" that all those backups blocks are in reasonable shape and the filesystem doesn't need checking.

One way of avoiding this is to do as others have said by using the "check=none" option to the mount command.

Another option that would have to be done by the empeg people is to originally make the filesystem with the "sparse superblocks" option. This just tells the ext2 "formatter" to not make so many superblock backups, which makes mounting large filesystems much quicker. (It also tends to make them less reliable overall since the fewer copies you have available, the more likely it is that a single corrupted copy will not be recoverable.) You can't do this yourself without reformatting your data partition...