I rotate backup drives.  With 2.4 kernels, I could hotswap PATA
(40 pin Parallel ATA IDE) drives directly, using hdparm to tristate
the bus.  2.6 doesn't permit this, so I use USB2 hot swap cages
instead (see http://wiki.dirvish.org/index.cgi?USB2Drives ).

I have been experimenting with SATA hot swap.  I will be keeping my
PATA drives for the next few years, but I can use a SATA to PATA IDE
bridge board (JMicron JM20330 chipset, about $20) to connect the PATA
drive to a SATA cable to a SATA board.  This works at the same speed
as direct connect PATA, 30MB/s, much faster than USB2 at 10 to 20MB/s.

I've been running a "mount-write-read-erase-unmount" loop, 100GB at
a time, about 1 hour per cycle, for the last 3 days with no lockups.
Some USB2 bridge chipsets lock up after 5-50GB of transfer.  I am
confident enough to try making backups through the SATA path.

Many different SATA-PATA bridge boards are available.  Perhaps some
of you would like to try some of the other possibilities.  With all
the different options, I expect some will fail, either immediately
or after a few hours, but it would help to learn what works.

If this does work, I may be ditching a bunch of USB2 hardware.

Keith

-- 
Keith Lofstrom          [log in to unmask]         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs