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Old Apr 4th, 2009, 03:29 PM   #1
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How long does 'erase free space' take to do it's thing?

I was silly enough to choose 7-pass erase on 69GB of free space. It's been going for 24 hours. How much longer might it take? Or should I risk aborting it?
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Old Apr 4th, 2009, 05:59 PM   #2
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Just abort it.
Just what IS on there??
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Old Apr 4th, 2009, 06:15 PM   #3
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Old Apr 4th, 2009, 09:31 PM   #4
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I have seen zeroing a 6GB HD run over night. So even with faster drives this is gonna take a very long time.

Unless we are talking psychiatric client files I really think 7 pass is over kill. A whole lot faster to just write the same jpeg file over and over a bunch of times.
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Old Apr 5th, 2009, 12:46 AM   #5
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Chances are there have been a few passes completed already. Disk Utility might even tell you (something like " ... erasing 3rd pass of 7 ..."). The point is, if it's been zero'd once or twice, it's probably fine, and at 24 hours it probably has more than two passes done, considering the size of the drive.

7x is for when you sell the drive and used it for banking, medical records, etc. 3x is probably enough for almost any drive; the tools needed to read it after that are really only owned by law enforcement, and actually using them really means they are investing thousands of dollars on reading that drive. Not likely just for grabbing your hotmail password, in other words.
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Old Apr 5th, 2009, 12:53 AM   #6
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Quote:
Originally Posted by gordguide View Post
Chances are there have been a few passes completed already. Disk Utility might even tell you (something like " ... erasing 3rd pass of 7 ..."). The point is, if it's been zero'd once or twice, it's probably fine, and at 24 hours it probably has more than two passes done, considering the size of the drive.

7x is for when you sell the drive and used it for banking, medical records, etc. 3x is probably enough for almost any drive; the tools needed to read it after that are really only owned by law enforcement, and actually using them really means they are investing thousands of dollars on reading that drive. Not likely just for grabbing your hotmail password, in other words.
I just did a 250GB drive in a fw case (zero once as a new erase of the whole drive) and it took between 4-5 hrs. I would have thought that a 69GB erase, even with 7 pass, shouldn't take that long? does Disk Utility not show you an estimated time remaining?

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Old Apr 5th, 2009, 01:06 AM   #7
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Might be on a USB 1.1 bus (or might inadvertently have a USB 1.1 device on the bus which will cause a 2.0 Bus to revert to 1.1 speed, or might have other devices using the bus) or be an IDE 66 or IDE 100 drive, for example.

I agree that 70 gigs in 24 hours is slower than normal, but it's within the realm of possibility, especially if the drive is older. It's also worthwhile to keep in mind that whenever you use any of the zero or multipass options you also force a check of the drive's sectors, and force mapping out of bad sectors. Disk Utility will try to read bad sectors a number of times before mapping one as bad, for example. It's slow.

Disk Utility will give you an estimate but it's based on how long the process has taken so far; any bad sectors discovered will cause that estimate to be wildly optimistic and erratic.

Going back to your example, a 4 hour zero means you can expect a 28 hour 7-pass; a 5 hour zero means 35 hours, a difference of 7 hours. That shows how much variance there can be even with a new drive in excellent condition with a good bus and inherent drive speed.

As it turns out, I'm zeroing a 500GB USB2 drive right now; it's listed as a 9 hour operation but I know there is one bad sector on the disk at roughly the 220 GB mark, so I expect it to take a bit longer.

Last edited by gordguide; Apr 5th, 2009 at 01:19 AM.
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Old Apr 5th, 2009, 04:16 AM   #8
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Thanks, everyone. I quit without any apparent detrimental effect, despite warning of likely dire consequences for the HD if I didn't leave Disk Utility to finish doing its thing. Now I'll erase-and-install OSX (again) so that I can command-Q setup assistant and leave the iMac ready for my niece to set it up herself.
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Old Apr 5th, 2009, 12:06 PM   #9
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As for my drive, I went to sleep with a reported 5 hours left, and it was done when I awoke the next "lazy Sunday" morning around 9:30 (I normally need 5~7 hours of sleep and wake up naturally, without alarms).

A check of Disk Utility's log reveals a start time of 10:59:xx PM, (" Disk Utility started") an end time of 7:25:xx AM (total: 8 hours 26 minutes) and a log entry "Secure Erase completed successfully in 9 hours." It then took an additional 15 seconds to format the disk.

There is no entry regarding a bad block (discovered via a file I could not read during the initial backup of the drive with LaCie Silverkeeper v2.x) and the final drive size is identical to it's original size.

I don't know if that means that there was no bad block and the refusal to read was some other corruption, or it it was found and mapped out. All Hard Drives have "secret" space to allow for a small number of bad blocks to be mapped out, and I'm told most drives ship with a few mapped out when new.

So, a Q for anyone ... would a bad block found show up in Disk Utility's log?
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Old Apr 5th, 2009, 01:09 PM   #10
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My late 2007 MBP has had a logic board and superdrive replaced and it still hangs and beachballs a couple of times daily. Apple ordered me a new MBP to replace this one and will call me when it arrives. They asked if I wanted them to transfer my data to the new MBP and I declined. I want to get a fresh start, so have my photos and music stored on an external and I will reinstall all my apps and files from the same external. I had hoped that way I would not be dragging any bugs over that may be contributing to this MBP's issues.

When I get the call it has arrived, which should be this week, I had planned on doing an erase and install with my original install disks before turning it in to the Apple store. Anyone see any problems with this method?
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