Why did SoftRAID lock my volume?

On very rare occasions, the Mac system software can get disks confused.  When this happens, reads and writes are meant for one disk get sent to a different disk instead. We believe this is a system software bug and have reported it to Apple. (It is in Apple’s bug system as #41327130.)

When the system software confuses two disks and these disks are part of a RAID volume, writes to the volume go to the wrong disk and the volume can become corrupted.

We have seen this with some user volumes and have added a feature to SoftRAID 5.7 to detect when the system software confuses disks with one another. When we detect this condition, we lock the volumes which use the affected disk and prevent all future writes to them. The volume will become writable again after the Mac is restarted, which clears the error condition in the system software. By preventing writes during the error condition, SoftRAID helps prevent volume corruption.