I have a 1.6 TB LaCie that runs internal RAID and is faster than my 500Gig Lacie (72 Mb/sec vs. 52 Md/sec) and have it partitioned as 3 500 gig sectors. I get the beach ball when saving a digitize, where I don't on the 500 Gig drives even though they are slower. All are connected to 800 Firewire and all drives are 7200 RPM. I think it must be something else because my bare 500Gig Lacie is the same size as each partition and I don't have the problem of waiting with the 500's.
Thanks
Charlie

Only thing I can think of are the drives are stopped when idle so you see the beach ball each time the computer waits for them to spin up.

You can set it in the energy saving system preferences panel, or eventually maybe in the software LaCie is furnishing if you used it. (unknown territory for me).

BTW, it's very bad for IDE drives to be spinned up and down all the time… They are not made for this unfortunately.

I've actually gone thru those settings. The drives are set to always spin, except for sleep, of course, and all the energy settings are never and high performance. It only happens on the 1.6 TB drives and not the 500 GB drives, and they are on the same buss.

Does it change something if you reverse the order ? If so, it's the bus, if not, it's the LaCie drive

If it's the bus, the easy solution (providing there's no hidden problem) is to use a dedicated Firewire PCI card. It's not that expensive, and it'll work better than Apple FW800 anyway. I remember vaguely of a problem when multiple FW800 HD are chained, it slows down, I have myself 3 Drives on one port, but if it is slowed down it's not noticeable in my use/config (icecube/pleiades enclosures).