Disk duplicators

[Bill McGonigle]

On Jun 18, 2005, at 18:56, Benjamin Scott wrote:

>   These days, with Hi-Speed USB-to-IDE adapters so plentiful, I wonder 
> if it wouldn't be cheaper and just-as-nice to just buy a bunch of 
> those and use "dd" or the like.

I've yet to try the multithreaded dd on a USB bus but the typical dd 
doesn't work well in this situation.  I'm not sure what the root cause 
of the problem is but I've had a 60GB laptop drive on a USB to IDE 
converter take 18 hours to image.  File copy performance from the same 
drive ran at about what you'd expect USB 2 to run at.  As there weren't 
any kernel errors triggered I've been assuming a timing issue between 
dd and the usb subsystem but I don't know that to be true.

I also use drive trays on an ATA/133 bus on the same system and dd can 
do about 17MB/s which for being single threaded is about right.  That's 
still 2 hours for a 120GB drive though.

Make sure to use a large bs= - on this system 32M is faster than 16M 
but 64M doesn't seem to help.  Maybe on an SATA setup it would.  The 
default 2K is abysmal.

You can't hotswap those IDE sleds on linux yet, but a reboot is so much 
faster than the USB bridge.  I have a firewire card sitting on top of 
the machine to try out next time I update the kernel.

Back in the day we had a Mac IIfx setup with 5 NuBus SCSI cards and 
we'd hook up 6 drives to each and image them all at once using one of 
the SCSI utility vendor's tool.  The bandwidth wasn't real high on 
SCSI-2 compared with today but the throughput was excellent.  Cool hack 
which you might be able to do with some 3Ware cards today.

-Bill
-----
Bill McGonigle, Owner           Work: 603.448.4440
BFC Computing, LLC              Home: 603.448.1668
bill at bfccomputing.com           Mobile: 603.252.2606
http://www.bfccomputing.com/    Pager: 603.442.1833
AIM: wpmcgonigle                Text: bill+text at bfccomputing.com

For fastest support contact, please follow:
http://bfccomputing.com/support_contact.html