[plug] USB2 or FW

hooker at iinet.net.au hooker at iinet.net.au
Wed Jun 30 14:55:50 WST 2004


Quoting Brad Campbell <brad at wasp.net.au>:
> 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.

Thanks Brad, very helpful! Interesting that you found USB2 slower than FW. I'd
heard exactly the opposite under Windoze. I agree about reliability though - 90%
speed and 100% right wins every time.

Hooker




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