Welcome to the MacNN Forums.

Lucy Gibbs · Apr 5, 2004, 06:51 AM

My computer crashed upon closing. When I tried to restart it just hangs on the grey loading screen. I have a G4 powerbook and am running OS X 3.x

I have tried the following:

Zapping the PRAM
Starting it in Safe Mode
Resetting Open firmware
And using the disk utility feature on the software install and repair CD which says it is fixing but then doesn't work
but did come up with the message: Overlapped extent allocation (which I think is the problem)

I also tried a file system check (fsck) didn't work - but did get an error message
After popping into the apple shop - they suggested that I try something called archive and install

However on reading more about this I see that this is a bad idea if you get an message in disk utility that says
overlapped extent allocation (I remember getting this message in Disk Utility) and archiving and installing just makes things worse

1.) If I erase and install would that work (even though it says I have overlapped extent allocation

2.) How do you get overlapped extent allocation - my Harddisk is hardly used I have only had the computer for 4 months and I have checked . . .

Please help I am getting desperate and scared. . .

Developer · Apr 5, 2004, 07:13 AM

Third party disk repair utilities might be able to repair the problem. It would then be safe to do an Archive and Install.

You could also completely reformat your hard disk and do a fresh install. Of course you can only do this if you have a recent backup of your data, or if you can mount the volume when booting from an other partition/external volume and then back up your user data.

Lucy Gibbs · Apr 5, 2004, 09:11 AM

Thank you for your advice. Can anyone explain to me what causes
"overlapped extent allocation" in order that I can avoid this in the future.

Visnaut · Apr 5, 2004, 10:58 AM

I doubt it's any more than a fluke occurence. That crash at shutdown might have spurred it, but that too may not be narrowed down to one single root cause.

One word of advice, though: If it happens again in the future under different circumstances, then I would seriously consider replacing your hard drive, as it may indicate a hardware problem.

bbales · Apr 5, 2004, 11:21 AM

Do a search on apple discussions.

This happened to me not quite a year ago. As I understand it, an overlapped extent allocation occurs when two files (or bits of info) are trying to occupy the same spot on your hard drive.

The only way I fixed it was by using Disk Warrior. I found 5 or 6 such instances. (And by the way, when I was buying it, several of the Apple people had never heard of this. The one guy who had said, fix it, posthaste. You could lose your whole drive otherwise.)

And actually, several months later the same thing happened again. I read somewhere that using Limewire can somehow cause it, but I'm not sure about that. At the time, I had used Limewire, but no longer do.

Running fsck does nothing, either. You need Disk Warrior. I'd order it ASAP. If you live by an apple store you could get it there.

Good luck.

Oh -- I'm still using the hard drive on which this happened. I've had no problems except for those two times. But I'm pretty religious about backing up.

stuffedmonkey · Apr 6, 2004, 05:42 PM

i used to work in one of those apple stores, and I would definately tell you an archive and install is a horrible idea id you have overlapped extents... The only two things that I would recommend to fix it is either Diskwarrior or erasing the drive. installing software on top of an already corrupt drive would make things worse!

bbales · Apr 6, 2004, 06:07 PM

Lucy -- Any word yet? Are you fixed? Sure hope so and that everything is OK>

Laurence · Apr 6, 2004, 06:22 PM

I was getting many of these errors a year ago or so and I finally fixed it by replacing RAM in the computer. In my case I ran FSCK about once a day and always got overlapping extents and they were always fixed, but they would come back the next day. I bought a new HD and had the same thing happen. Finally, after 6 months of dealing with random crashes and other issues someone suggested I test the RAM in OS 9 using a utility that I can't remember right now... I think it was Gauge Pro from Newer Tech... I tested and determined that the RAM was bad. I replaced all the RAM as it was cheap at the time and for the last 9 months I have not had one crash or disk error of any kind. I still run FSCK every time I reboot (once a month or so) and have never found anything wrong.

This may have nothing to do with your issues, but if it continues to happen, test the RAM. OS X seems to be more sensitive to bad RAM than any other OS I've ever seen. but with the replacement RAM from Crucial I have never seen an OS as stable.

Detrius · Apr 6, 2004, 07:31 PM

Originally posted by Laurence:
This may have nothing to do with your issues, but if it continues to happen, test the RAM. OS X seems to be more sensitive to bad RAM than any other OS I've ever seen. but with the replacement RAM from Crucial I have never seen an OS as stable.

The only reason OS X is more sensitive is because it uses more. Therefore, it is more likely that OS X will actually access bad RAM.

tooki · Apr 7, 2004, 02:13 AM

That is not correct.

The order in which memory is accessed can affect its reliability. That's why old memory tests for core memory were custom-written for each model, and tested not just whether they could accurately reproduce any given bit, but whether they could do so under different conditions. Modern RAM tests don't do this, but OS X's memory access, which by nature will be somewhat different from OS 9's, could expose RAM problems that had gone undetected before.

Anyway, overlapping extents are just a type of disk corruption (one that can be symptomatic of data loss, unfortunately). It does not, in ANY way, indicate existent or imminent hardware failure, as Visnaut suggested. The crash you describe is exactly the kind of thing that causes such corruption.

Just buy and run DiskWarrior to fix the problems, and then in the future run DiskWarrior now and then to fix any budding problems before they cause data loss. To the same ends, also be sure that journaling is turned on.

tooki

Lucy Gibbs · Apr 7, 2004, 04:04 AM

Thank you for all your advice. I am not in a position to buy disk warrier at the moment so I am going to erase and install tonight and hopefully that will work. Luckily I have a recent back up of my data.
Hoping that this will solve the problem.

Many Thanks

Lucy Gibbs · 04:48 AM

I erased and installed - which worked but . . .

1.) The Capacity of my Hard Disk is showing as 55.9 GB (I'm sure this is too little)
Available space is showing as 52.8GB I have only installed the operating system I'm sure there should be more space than this? What has happened to the 4GB of space? I know that it won't read 60GB but I'm sure it should be closer to that 55

Any advice gratefully received