Something like this?

#! perl -slw
use strict;

$/ = 'Drive';

while( <DATA> ) {
    print "$1 : $2" if m[(Tray .*?)\nRaw capacity: (.*?)\n.*Unassigned
+]s;
}

__DATA__
Drive at Tray 0, Slot 1
Raw capacity: 68.366 GB
Usable capacity: 67.866 GB
Current data rate: 2 Gbps
Product ID: ST373453FC
Mode: Assigned
Drive at Tray 0, Slot 2
Raw capacity: 68.366 GB
Usable capacity: 67.866 GB
Current data rate: 2 Gbps
Product ID: ST373453FC
Mode: Unassigned
Drive at Tray 0, Slot 3
Raw capacity: 68.366 GB
Usable capacity: 67.866 GB
Current data rate: 2 Gbps
Product ID: ST373453FC
Mode: Assigned
Drive at Tray 0, Slot 4
Raw capacity: 68.366 GB
Usable capacity: 67.866 GB
Current data rate: 2 Gbps
Product ID: ST373453FC
Mode: Unassigned
Drive at Tray 0, Slot 5
Raw capacity: 68.366 GB
Usable capacity: 67.866 GB
Current data rate: 2 Gbps
Product ID: ST373453FC
Mode: Assigned
[download]

Output

P:\test>junk3
Tray 0, Slot 2 : 68.366 GB
Tray 0, Slot 4 : 68.366 GB
[download]