Q about SoftRAID 3 & splitting mirrors as part of a backup strategy

SoftRAID 3 software, which I do not own & have not tried, seems to have a nifty feature that seems to solve a problem I have.  I'm writing to find out from those who have actually used SoftRAID to find out if it actually will do what I want.

First, some background.  I currently have about 55 GB (in 1.5million files) of email to be backed up.  I have been shutting off the email software before performing the backup and turning it back on when it's finished.  I use BRU Server for backups to a an external Firewire 800 disk.  The full backup takes more then 11 hours, which makes me uncomfortable because the email is off that whole time.  Incremental backups (a GB or so & hundreds of thousands of files) can take a couple hours, which is still a lot of time for the email to be off.

I've been trying to think of ways to minimize the down time of the email, and I thought of a situation where the mail store could be stored on a RAID 1 volume and temporarily split while the backup happens.  One half (the primary half) would be re-mounted (or continue to stay mounted - not sure how it works) as the mail store and the email software would be turned back on.  The other half is mounted as the volume from which the backup would come from.  After the backup completes, a script would re-combine the two halves, and the RAID software would rebuild the mirror, considering the primary half as the "good" half.  From reading, it seems that Apple's RAID software doesn't allow for splitting a mirror.  The SoftRAID company web site says that their software allows for splitting a mirror.  My questions to those who have used SoftRAID are:

1)  When a mirror is split, are both halves mountable and, if so, what are their volume names?  

2)  Is there a command-line tool for splitting the mirror, so that it can be used in a script like I envision for my pre- and post-backup script?

If anything does something similar to what I would like to do, could you please let me know if it is a workable idea?  Thanks.