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You are here: MacNN Forums > Software - Troubleshooting and Discussion > macOS > "overlapped extent allocation"-is that serious?

"overlapped extent allocation"-is that serious?
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thickdrummer
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Sep 27, 2006, 03:15 PM
 
I've had a couple of error messages show up after a restart, reported by TechTool Pro, and by the sounds of it, OS X decided it couldn't be bothered writing to the free space on my HD so it started writing over stuff that was already there.
Is there any way to fix this or am i facing a re-install?
If i need to reinstall is there anyway of getting 10.4.1-10.4.7 on a disc to install? I bought tiger when it was released so I'm probably facing hundred of megs of data to download to update from 4.0 to 4.7 right?

Anyhoo, I think i gave my PowerBook a beating so its getting its own back...I have hundreds of apps, preferences and third-party thingy-majiggys installed. Could this have caused my problems?

Any advice is welcome...Cheers people
( Last edited by thickdrummer; Sep 27, 2006 at 04:06 PM. )
     
reader50
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Sep 27, 2006, 05:22 PM
 
'overlapped extents' means two (or more, usually two) files are claiming some of the same blocks. As you have apparently figured out, one file has partially written over another. This isn't good, and at least one of the files will be toast.

Pick up Diskwarrior. It will fix you up without needing a reinstall. It can save your bacon later from much more serious problems too, so it is a good insurance investment regardless.
     
thickdrummer  (op)
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Sep 27, 2006, 06:11 PM
 
Thanks for the reply.

I have TechTool Pro but I can't find any info on how to resolve the problem, although saying that, I haven't seen any errors for a couple of days.

I think I'm ready for a reinstall anyway...I've had so many apps on it that there's random files all over the place. Plus, some crappy modem software wiped my entire documents folder...I thought my back-up had completed, but i never set it off...and for some reason TTP couldn't recover it. Gutted.

Anyway, will I need to download 10.4.0 to 10.4.7 in its entirety ?
     
reader50
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Sep 27, 2006, 07:06 PM
 
Reinstall 10.4.0 from disk. Then just download the 10.4.7 Combo Update. Afterwards, run Software Update to get any other assorted fixes. You'll find a QT update, a Security Update or two, some app updates (Safari, iTunes, etc) and a whole mess of iPod updates, regardless of if you own an iPod or not.
     
MM-o4
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Sep 27, 2006, 07:45 PM
 
yeah I have had probs with overlapping files before. Took DW ages to fix, and on one occasion it did fix it. But it work a shot if you don't want to erase and reinstall.

Good luck

MM
     
CharlesS
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Sep 27, 2006, 08:41 PM
 
How much free space do you have? I usually see overlapped extent errors on hard drives that have been filled to the brim.

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Detrius
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Sep 27, 2006, 09:59 PM
 
BEFORE YOU REINSTALL, BACKUP YOUR DATA AND REFORMAT!

Do NOT reinstall without fixing the overlapped extents. If you don't fix this, it will get worse. There are two ways I know of to fix this: DiskWarrior or format. Worst case scenario is bad blocks.

An OS reinstall without fixing this issue will wipe ALL of your data. Don't do it.
ACSA 10.4/10.3, ACTC 10.3, ACHDS 10.3
     
steve626
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Sep 28, 2006, 12:30 AM
 
Originally Posted by thickdrummer
I think I'm ready for a reinstall anyway...I've had so many apps on it that there's random files all over the place. Plus, some crappy modem software wiped my entire documents folder...I thought my back-up had completed, but i never set it off...and for some reason TTP couldn't recover it. Gutted.
Sounds like you live a bit on the wild side. I know it's sort of not your main concern, but ... there's "crappy modem software" out there that "wiped [your] entire documents folder"? That's kind of astonishing, can you let everyone know what this software is called? Sounds like poison.

Since your entire documents folder was wiped and you never backed it up, and you think the "hundreds" of apps are causing problems, maybe it's not such a bad idea to reformat (slow method, writing zeros) the entire drive and then reinstall Mac OS X. Probably should be more selective about what apps you install in the future?

If you are using a modem, you can probably get a local store to download for you the combo update to 10.4.7 and burn it on your own CD. Might take several hours to download over a modem.
     
frdmfghtr
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Sep 28, 2006, 04:44 PM
 
As long as you're going to reinstall the OS, you might consider upgrading the hard drive while you are at it, if you see a need and the budget to do so. Kill two birds with one stone.
     
Detrius
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Sep 29, 2006, 03:48 AM
 
Originally Posted by steve626
...maybe it's not such a bad idea to reformat (slow method, writing zeros) the entire drive...

Myth. The only way writing zeros to the drive is going to help is if you have bad blocks. If you have bad blocks, you need a new hard drive. He has TTP. If the bad blocks hadn't yet been mapped out, a surface scan with TTP will identify them. A drive that has acquired bad blocks since leaving the factory is unreliable and should not be trusted. Period. You could use a drive like that for storing a bunch of downloaded software updates, but you shouldn't put irreplaceable data or an operating system on it.

The process of zeroing the data also maps out bad blocks if possible. Beyond that, there will be absolutely no speed difference between zeroing data and not zeroing it. None. If someone noticed a difference, they had bad blocks.
ACSA 10.4/10.3, ACTC 10.3, ACHDS 10.3
     
reader50
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Sep 29, 2006, 04:27 AM
 
There is another reason to format with the zero-all-blocks option. If you sell or give the computer to someone else, it is the only sure way to make your own files unrecoverable.
     
P
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Sep 29, 2006, 07:53 AM
 
To the OP: Copy your data to another drive, reformat and reinstall. Fixing an error like that with a directory repair tool is only a band-aid. You can do it now, but eventually you will have to reformat. Sorry.

Detrius: I wouldn't say "Myth" so much as "outdated information". There was a time (also known as mid-eighties) when a low-level format could be used to reliably map out bad sectors without that being an indication of a bad drive batch. These days, it's better to get a new drive from warranty, becase a drive that develops bad sectors is a defective product. That the option is still there is for the situation that reader50 describes: To permanently wipe a drive before resale.
     
G Barnett
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Sep 29, 2006, 03:45 PM
 
Originally Posted by reader50
There is another reason to format with the zero-all-blocks option. If you sell or give the computer to someone else, it is the only sure way to make your own files unrecoverable.
I think I'd prefer a program that would 1) generate a random string of eight 1s or 0s, apply them to the first data byte of the hard drive via a logical NOT operation, then 2) repeat the process for each byte on the drive and 3) do the whole thing for like 8-10 passes on the drive. Random bit-flipping for the win!

Even include an option for drives that are to be disposed of, where it does the same thing to the driver partition AND to the firmware, making the entire drive utterly unusuable from that point on.

Doubt any such beast exists, tho.
     
bbales
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Sep 29, 2006, 04:19 PM
 
I have had this problem twice, both several years ago -- Disk Warrior fixed it nicely. I read later that LimeWire somehow caused it -- I'd used it a few times but have long thrown it out. I'm not sure how the program could have caused it either, but that's what I read.

Anyway, DW fixed the problem. I've not had it since. And no need to wipe the drive and start over, either.
     
reader50
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Sep 29, 2006, 05:09 PM
 
Originally Posted by G Barnett
I think I'd prefer a program that would 1) generate a random string of eight 1s or 0s, apply them to the first data byte of the hard drive via a logical NOT operation, then 2) repeat the process for each byte on the drive and 3) do the whole thing for like 8-10 passes on the drive. Random bit-flipping for the win!

Even include an option for drives that are to be disposed of, where it does the same thing to the driver partition AND to the firmware, making the entire drive utterly unusuable from that point on.

Doubt any such beast exists, tho.
In practice, writing zeros once is effective. In theory, some of the data could be retrieved, but not by the drive's existing electronics. The retrieval process is so impractical that the average user doesn't need to worry about it.

You would need to dissassemble the drive, and at the very least, replace the control electronics. Possibly the heads as well. You would need analog amps on the read heads, and adjustable circuitry that would try to capture magnetic values only slightly above zero. The standard electronics built in will call any low value a zero, and only a high value as a one.

You'd still have a lot of random bit errors. Retrieved applications would not run, and complex files wouldn't open due to corruption. You could read text files manually, and possibly sift through a DB with a hex editor to retrieve slightly-typo'd data.

This would be more involved than what the Drive Savers people do, and they often run a few $K to scavenge a drive. So in theory, a single zero pass could be undone, but for a price of perhaps $10K per drive.

If you still want to make retrieval impossible, go to Disk Utility and when you are ready to Erase, click the Security Options... button. There, you can select the radio button to do a 7-pass random overwrite. This works good for government laptops after you steal them, so that no classified data escapes through the black market. It also works good as an endurance test of modern hard drives - the drive could be busy for the next 24 hours.

If you are feeling really paranoid, you could choose the 35-pass random overwrite option. That will give you plenty of time to make your psych appointment.

Seriously, I read somewhere that those options meet government specs for scrubbing classified info. There is no need to wipe the partition map, nothing there besides partition sizes and names. Both of which can be overwritten if you repartitioned the drive.
     
CharlesS
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Sep 29, 2006, 05:18 PM
 
Originally Posted by P
To the OP: Copy your data to another drive, reformat and reinstall. Fixing an error like that with a directory repair tool is only a band-aid. You can do it now, but eventually you will have to reformat. Sorry.
Actually, what the utilities do is the same thing as what reformatting would do if you backup first - copy the overlapped files to new locations, then delete the originals.

Ticking sound coming from a .pkg package? Don't let the .bom go off! Inspect it first with Pacifist. Macworld - five mice!
     
   
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