Disk Repair

[jb]

iMac G5 rev.A OS 10.4.8

On my Internal disk, I have 2 partitions:
1- OS 10.4 (OS 10.4.
2- OS 10.3 (OS 10.3.9)
On my External disk, I have 4 partitions:
1- Backup of my Internal disk 10.4.8 partition. (Which is backed-up once a week at 3 am on Monday mornings.)
2- PC (with OS 10.4. for my PC Emulator.
3- Archives.
4- Copies of previous(OS 9) and current(OS X) Apps.

On a sort of monthly or bimonthly basis, with Apple's Disk Utility, I repair Permissions (on those partitions with OS's) and Disks. Every time everything is normal, except this time. Using my Backup volume as the Starting Disk, my 10.4 partition Repair Disk window reads the following:

"Verify and Repair disk “10.4”
Repairing disk failed with error Could not unmount disk"

I tried OnyX (latest 1.7.8b2), and it says:
"Volume verified. The startup volume appears to be OK."

Who should I believe, OnyX or Apple's Disk Utility?

Or should I be concerned? Everything runs absolutly perfect and normal on my 10.4 partition.

jb

[Xairbusdriver]

Until a real expert comes along...

First, I don't think OnyX, Cocktail, or any other shareware app does anything more than run the built-in functions that that DU also uses; they are simply GUI front-ends for the built-in UNIX commands. Diskwarrior, TechTool probably do perform these and other tasks a little differently.

Second, the "Could not unmount disk" notice may be a clue that you either didn't actually have the external partition running as the Startup Disk or ( more likely ) that the actual DU that you ran was on the disk it was trying to repair. That may explain why OnyX said things were fine; you actually ran the OnyX that was on the external partition.

If you'd like, send me your whole setup and I'll test it for a few months. Meantime, you can use on old 'tray-loading' iMac I have in the attic!

[kelly]

If it happens again, try restarting and check it.

[jb]

Thanks XABD and Kelly.

XABD. I ran the Disk Repair from my 10.4 Backup partition, i.e. I had selected it as my Startup Disk, and ran it on my 10.4 Internal Volume. Thanks for the swapping offer, but I think I will be able to live with what appears to be a bug in the latest version of the Disk Utility. Read on.

Kelly. Well here is what I did.
- I selected my Internal Disk 10.3 Volume as my Startup Disk, and ran Disk Repair on my Internal Disk 10.4 Volume. The Repair window showed the 10.4 Volume as having been repaired and appeared OK.
FYI. The Disk Utility version on my Internal Disk 10.3 Volume is 10.4.4 (V145.7).

- I then selected my External Disk 10.4 Backup Volume as my Startup Disk, and ran Disk Repair on my Internal Disk 10.4 Volume. The Repair window again showed "Verify and Repair disk “10.4” Repairing disk failed with error Could not unmount disk".
FYI. The Disk Utility version on my External Disk 10.4 Backup Volume is 10.5.6 (198.12), which of course is the same version as the one on my Internal Disk 10.4 Volume.

I will not pursue this matter any longer as, as I wrote in my initial topic, everything runs absolutly perfect and normal on my Internal Disk 10.4 Volume.
 
jb

[Gregg]

That sounds frustrating. But, what can you do? As you say, as long as it works....

[tacit]

When a disk repair program repairs a disk, it must "unmount" a disk. "Unmounting" a disk is the same thing as "ejecting" it, in a manner of speaking; it means removing it from the desktop. When you drag the icon of a disk to the trash, you are unmounting it.

Disk repair programs have to unmount a disk because even if you believe your computer is sitting there doing nothing, it is always accessing and modifying disks that are sitting on the desktop. Spotlight is indexing them, other system level programs are accessing them--it never stops. A disk can not be repaired while something else is changing it.

"Could not unmount disk" is a common error message to see in Disk Utility. It means that the disk could not be removed from the desktop. There are two reasons why this might happen:

1. You have a file or a program or a font open that lives on that disk; or

2. The computer is using that disk.

If you are sure you have no files open on the disk, then the most likely explanation is Spotlight. Spotlight is constantly accessing disks. Every now and then, when you go to unmount a disk, Spotlight is in the middle of something that can not be interrupted, and will refuse to allow the disk to unmount. In those cases, if you try again and again, eventually it will unmount.

The message you saw from Disk Utility, with I think is badly worded and misleading, did not tell you that there was something wrong with the disk. It told you that it did not even check the disk at all because it could not be unmounted. If you wait about five or ten seconds and try again, it will probably work.

[Al]

I just had this happen yesterday.  It was a start up item using a file on that particular partition.  I didn't need that item to start up everytime so I removed it from the list, restarted my Mac and could then empty the trash.  the culprit in my case was Palm Desktop something something....

[jb]

OK, one more round!

Thanks tacit for an answer most instructive, and to the point as usual. Your explanation about Spotlight is probably most relevant as it is part of Tiger. That would explain why Disk Utilities on my Internal Disk 10.3.9 Volume, which does not have Spotlight, was able to repair my Internal Disk 10.4.8 Volume.

But then how does one explain that I am able to repair my External Disk 10.4.8 Backup Volume with my Internal Disk 10.4.8 volume?

I did try several times, a dozen or so at various intervals, to repair my Internal Disk 10.4.8 Volume with my External Disk 10.4.8 Volume with the very same message, "Verify and Repair disk “10.4” Repairing disk failed with error Could not unmount disk".

Yet It would be most interesting to find out why I get the message
1- "Verify and Repair disk “10.4” Repairing disk failed with error Could not unmount disk".
when I try to repair my Internal Disk 10.4.8 Volume with my External Disk 10.4.8 Volume,
and get the message
2-  "1 HFS volume checked No repairs were necessary".
when I repair my External Disk 10.4.8 Backup Volume with my Internal Disk 10.4.8 Volume.

FYI. My External Disk 10.4.8 Backup Volume is an exact bootable copy of my Internal Disk 10.4.8 Volume made with Super Duper version 2.1.3.

And just to make sure that something might have changed since last Sunday morning, I just made a fresh copy of my Internal Disk 10.4.8 volume unto my External Disk 10.4.8 Backup Volume.
Same results as in 1 and 2 above.

Al. I checked my System->Prefs->Account->Login Items. They are exactly the same on both my Internal Disk 10.4.8 Volume and on my External Disk 10.4.8 Backup Volume, as they should.

jb

[krissel]

One last thing you could try is to first boot to the external. Then physically dismount the internal 10.4 by dragging its icon to the trash. Then open Disk Utility. You will see the 10.4 greyed out but you can still run the Verify/Repair procedures on it. See what happens.

[Al]

Hey there jb,

Tacit hit the nail on the head, it was what happened to me.  As I found out a start up item was using a file on another partition.  that other partition could not be dismounted until I did what I stated above.

This is wierd, but, I've seen this happen using Carbon copy cloner before.  After making a copy of your start up drive when booting into that new start up drive some items are rediected to file/s on the original drive partition.  Never had this happen using Superduper.

In my case, I never had that same problem as you until the other day.  I never opened my Palm Desktop program for a long while until the other day and upon opening it, it automatically stuck something in my start items list that when I rebooted it went for a few hidden files in my Palm folder on the other drive/partition!  

Have you recently installed something?

[tacit]

I did try several times, a dozen or so at various intervals, to repair my Internal Disk 10.4.8 Volume with my External Disk 10.4.8 Volume with the very same message, "Verify and Repair disk “10.4” Repairing disk failed with error Could not unmount disk".

Most likely, the external disk is still loading something--perhaps a font or some startup program--from the internal 10.4. If you make an exact clone of one system to another drive, sometimes when you boot from that second drive, it will still try to launch startup items or fonts from the original disk, because sometimes programmers get lazy or make a mistake and include the name of the volume in the path to a file.

When you boot from your external hard disk, it's still loading something from the internal, which is why you can't unmount it.

[Gregg]

Ah ha! Disk Gymnastics could fix that. Now I have to go invent it....

I'm gonna be a millionare again, and I don't even have to respond to an e-mail.

Did anyone win the Powerball last night?

[jb]

Problem resolved!

First tried krissel's suggestion. That did not work.

So what I did was to erase my Internal Disk 10.4.8 Volume and, using SuperDuper, copied my External 10.4.8 Volume to my Internal Disk 10.4.8 Volume partition. And voilà! My External Disk 10.4.8 Disk Utilities was able to Disk Repair my Internal Disk 10.4.8 Volume.

I can only guess that by erasing my Internal Disk 10.4.8 Volume, it also erased whatever it was that was still loading from my Internal Disk 10.4.8 Volume.

FYI. Before this occured, the only new software that I had added was the latest Onyx 1.7.8b2 update.

Thank you all. Yet another example of unparalleled cooperation from TechSurvivors!

jb

[krissel]

Erasing the internal eliminated any inconsistencies of course. Sometimes that is the only way to get rid of a vexing problem. Reminds me of that 'Folder from He**' that I couldn't empty from the Trash. No Terminal commands or any app could do it. Only thing that worked was erasing the drive.