[plug] USB2 or FW

[Brad Campbell]

hooker at iinet.net.au wrote:
> I'm looking for some advice.
> 
> I'm considering an external cabinet with hot-swap disk for backups, and I'm not
> sure whether to go with USB2 or Firewire. I know that the nominal transfer speed
> is pretty similar, but does anyone have experience of how Linux handles USB or
> Firewire connected disks? Particularly with bulk data transfers. Are there any
> gotcha's that I should be aware of.
> 

for USB2 stay away from anything with a GeneSys Logic chip in it, and it looks like Cypress Semi as 
well. Most others seem to be ok.

Firewire is pretty good now in 2.4 and late 2.6 kernels. Go for an Oxford Semi chip if you can as 
they are the most solid under linux. (A low of external FW boxes use the Oxford chip)

If using FW under a 2.4 kernel make sure you grab the patch of linux1394.org to enable effective 
hotplugging of FW disks. It just works under 2.6
For large data transfers, make sure serialize_io=1 on the sbp2 driver (It now defaults to that but 
I'm not sure if the patches have made the official kernel yet).

I have used USB2 and FW with 8 external disks to back up over 1.4TB of stuff and have had much 
better, more reliable results with FW. I also have some horror stories of silent data corruption 
with USB2.

Like write 100GB to the disk and then verify it to find corrupt data. No errors in the logs or any 
form of messages to report that the data was being corrupted.

No such problems with FW.
I do get 20MB/s with USB2 and only 17MB/s with FW, but to my mind reliable data transfers beat speed 
any day of the week.


Regards,
Brad