Mac OS X has, in its disk utilities, a disk formatting tool. Interestingly, it has the facility to do a "Secure Erase" 7-pass option that claims to meet DoD requirements.
I inherited an external drive that I'm going to use for my "Time Machine" (another Mac OS X tool, for on-going incremental backups) volume. Because the drive came from someone else and clearly had some of their business-sensitive data on it, I decided to exercise this Secure Erase option.
It is a 2003, USB-2, 7200 RPM Maxtor 5000LE disk with 81GB of total capacity.
The utility is estimating this wipe (x7) and format operation will take seven hours. As a point of comparison, I set up a Win 2003 Server yesterday, with a 200GB internal disk. Formatting from blank to NTFS (default 4k sectors) took about 20 minutes (un-timed, but it was about that).
I have to guess that because the Apple secure wipe does write random bits to the disk, that there's considerable traffic over the USB--enough to absolutely fill the disk seven times. To get 'er done in 7hours, the Mac will have to spit/read 12GB/Hr, or 200MB/m or or 17.3Mb/sec. This is at the high-end of the "Full Speed" 12Mb/s for USB 1.1/2.0 spec (but well below the 480Mb/s for "Hi-Speed").
Which makes me think that the Apple & Maxtor USB implementations are very good, or, more likely, that the utility has done space/spec math on the USB xfer rate and posted that as the time estimate to be able to finish formatting the disk.
Maybe I'll get some "Hi-Speed" out of the Mac interface. The Maxtor specs say the 5000LE supports it, and the disk is 7200, as printed on the case, regardless of what the PC Magazine article says about only the 120G versions having the higher-speed spindle.
Ah! I just glanced over and whilst writing this post, the timer has fallen to an estimated 6hrs remaining for this task. Faster than spec, indeed.
Thursday, June 5, 2008
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