Connecting multiple external HDD

[RNKIII]

Long question, hopefully, shortened considerably...

I am currently using a 20" Intel iMac with OSx 10.6.1, 6Gb of memory, and a 640Gb internal hdd.
There are 4 powered external HDDs Daisy Chained to the single FW800 plug available from the computer.  All are OMC Mercury Elite Pro drives.

1st, is a 1 Tb drive that I utilize as my Time Machine backup.

 - - -> DC'd to that, via a FW800 cable is a 250 Gb drive that I currently do my Super Duper! backup to on a regular nightly basis.

 - - - - - -> DC'd to that, via a FW400 cable is another 250Gb drive not currently in use or turned on.

 - - - - - - - - -> DC'd to that, via a FW400 cable is a 120 Gb drive that I use for 'misc' data, it also is not turned on on a regular basis.

I know that 'turning on' the FW 400  connected drive(s) will lower the whole series to FW400 speed.

End of info....   Question...  

Is it some how possible to make my computer, and by extension SD!, think that the two 250Gb drives is a single 500 Gb drive???

The reason I ask, is that even though my internal is CURRENTLY no where near 250Gb usage, I am reasonably sure that it will expand to that point in the not too distant future, and I want SD! to have enough capacity on the external(s) to be able to function.


TIA,

Bob K.   rnkiii

[Paddy]

In theory, it appears that is possible - you'd need to run the two externals as a RAID 0 striped array. RAID 0 is not something I'd want to rely on for a backup though - if one drive fails, the RAID fails and say goodbye to your backup. Dave Nanian doesn't think a lot of that idea either:

http://www.shirt-pocket.com/forums/showthread.php?t=2971

Apple RAID info here: http://support.apple.com/kb/HT2559

Me? I'd just get another bigger drive for the FW800 enclosure (750GB perhaps - but at least 640GB). If the enclosure is one you bought yourself, no issues - if it's a pre-assembled external drive then you'll probably void the warranty by switching out the drive. I would assume, though you should check, that the drive is an SATA drive. If not, I'd just forget about it entirely and buy a new enclosure and a new drive, since the largest ATA drive you can buy these days is 500 GB.