A sparse image or sparse bundle question in relation to a NAS

Hi all,

I want to create a sparse image or bundle on my Synology DS713+ NAS to store my iPhoto and Aperture libraries.

The reason for a sparse image or bundle lies in the fact that both iPhoto and Aperture very much like a solid Mac Journal formatted drive to operate on.

Because I use an iMac and a MacBookPro I want these libraries available for both computers, and while they reside on a NAS they are 'automatically' backed up, and acessible to both computers.

I've tried storing the iPhoto library on the NAS directly (not Mac formatted but some Linux format, nót FAT32 anyway), but this was performing very poor (copying the library took hours and hours), and I've read on many NAS and Synology forums that this is not the way to go. The best solution I've read from these forums is to create a Sparse Image or Bundle on the NAS to benefit fully form an iPhoto or Aperture Library.

Now I have created a Sparse Image, and mounted it, and moving (copying) an iPhoto Library to it is done in a snap (amazing).

But having the Sparse Image mounted on my iMac, I cannot acess it on my MacBookPro unless I first umount it on the iMac, and then mount it on the MacBook.

Is there a way that such a Sparse Image can be mounted on more than one computer at the same time. In my case, mounted on both the iMac and the MacBook?

Or must it specifically be a Sparse Bundle to accomplish this, or maybe some Terminal wizzardry to get this done?