sudo dd if=/dev/rdisk0s2 of=/dev/null conv=noerror
(Sample...) dd > 25.4% > 0:12.57
3820858880 bytes transferred in 1473.733713 secs (2592639 bytes/sec)
I note that example 3, which was not run to completion, extrapolates to 10,310.14488 secs (171.835776 minutes) for the full 25Gb, close to a staggering 29 hours for my entire 250Gb HD, and that my HD temperature was the highest I've ever seen it while it was running.
aaaand that's what you get when using the default block size of 512 bytes. It's a new call to DD every 1/2 kilobyte - of which there are 448 million on a 250gb HD. Although it surely heated up your CPU, the hard drive probably didn't notice a thing.
You should also note that you were not scanning the entire drive. "s2" refers to a partition on the drive. (though probably your main HFS partition, so MOST of the drive for sure, but can miss BAD things like IO errors in the partition map or boot block)
Latest version of my surface scanner is
here if you want to check it out.
Considering the very small overhead involved in doing a properly blocksized scan in bash, I'd expect my script and techtool to be within less than a minute of each other on a full scan of a 250gb drive.
You
NEED to remove the "conv=noerr", otherwise dd
will not stop on io error.
