Timothy Standing of SoftRAID writes:
We have started to see a number of users (so far 8) whose SoftRAID volumes are no longer mountable after they upgrade to 10.7.4.
Looking through the kernel.log file, there is an error being returned indicating that some call is not supported (the file system isn't supporting it). My estimate is that 2 - 5% of users with SoftRAID or AppleRAID volumes are going to encounter this bug.
There are two interesting points:
1). If the user moves the disks to another Mac running 10.7.4, they often mount and,
2) If they convert their SoftRAID volumes to AppleRAID ones, they often encounter the exact same error.
It might be good for you to advise your users to hold off updating to 10.7.4 until this issue has been resolved. There are also reports of PGP Disk volumes not mounting after upgrading to 10.7.4. I don't know if this is caused by the same bug or a different one.
MPG: I haven’t had issues so far with OS X 10.7.4, but every OS update carries some risks.