Delay services until external drive mounts?

Question

I have a Drobo 5D connected to my Mac running OS X Server. I use my Drobo to host the "Service Data" folder. For the most part, this has been a great setup, however - in the event of a cold-start, I need my OS X Server to delay starting services (mainly mail server) until the Drobo is mounted.
In a cold start scenario, my Mac boots and is ready to go before my Drobo has completed its power on initialization (particularly in the event of a power outage). When this happens, the Drobo is not mounted when OS X Server starts the mailserver. Since the folder "/Volumes/Drobo" can not be found, OS X creates it with owner "_dovecot" (the mail service uid). When my Drobo becomes ready, it mounts under "/Volumes/Drobo 1" ... this results in the mail service storing my mail in an invalid location, and the remainder of my services (time machine server) not being available.
Is there a way to delay the start of the mail service until the drive is mounted? Or even just to introduce a time-delay? If I put a 5 minute delay, it would be more than sufficient.
Thanks!
(Note: this is OS X 10.9.1 Server... I accidentally tagged it Mac OS 9, and my update doesn't seem to take affect)

Answer 1

Caveat: I have not tried altering the startup delay setting via the systemsetup command-line command, but it looks to be close to what you want.  Here are the applicable parts of the systemsetup man page:
systemsetup
     -getwaitforstartupafterpowerfailure
             Get the number of seconds after which the computer will start up after a power failure.
     -setwaitforstartupafterpowerfailure seconds
             Set the number of seconds after which the computer will start up after a power failure. The <seconds> value must be a multiple of 30 seconds.
Here's an example of fetching the current delay value from an OS X Mavericks box;
$ sudo systemsetup -getwaitforstartupafterpowerfailure
Password:
getwaitforstartupafterpowerfailure: 0 seconds
$
Based on your requirements and the description, maybe 300 seconds waiting for the disk to come online and to finish whatever RAID rebuild or controller initialization is necessary here would be the obvious test.
See if it works.  (Please let us know, too.)
Possible hardware options include sequencing power strips (power bars), but those aren't cheap; US$300 seems to be typical for one of those, and the ones I've located (Middle Atlantic) don't have delays anywhere near as long as your environment seems to require. 
Sequencing this startup from another system via a network-connected power strip — those tend to be a little over US$100, last I checked — would also be feasible; if you have another box (Mac, Linux, PC, Plug Computer, whatever) that can power up and manage the network power strip for you.