External Drive Master Files Offline

Hi

I used to store all my master files on a single external drive(VolumeA). Recently I've purchased a new external drive(VolumeB) and I intend to store my new masters files into the new drive while keeping the old ones in the old hard drive. I import the photos using aperture like how I did previously.

So, I noticed that each time I disconnect VolumeB and reconnect it again, the images that I stored in VolumeB appear to be offline in aperture. I have to relocate the master files each time I disconnect VolumeB. VolumeB appears to be offline each time in the top section window of relocating reference files dropbox.
On the other hand, I tried importing master files into VolumeA and did the same thing(disconnecting and reconnecting), the images are still online.

Has anyone encounter this before? What should I do to make my volumeB appear online to aperture each time i connect it(since I will importing all my new files into it)?

Thanks lot!

Kin

Message was edited by: Kin munn Tham