Surface scan on the other hand is slow no matter what utility you are using.Unless you're one of the smart lads that has their computer doing a slow surface crawl continuously
I have about a dozen drives here under that level of protection, and recently though I've been having problems with one specific drive whose throughput drops below 1mb/sec when certain rsync backups are running on it. Wish it wouldn't do that, I'm getting tired of the warning emails.
In the last year it's tagged two 1tb ext usb drives that were getting ready to die, and in both cases I've been able to get a replacement drive in the building before the drive finally died. (even with backups I prefer to know my drives are healthy)
