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Beachballing and "disk0s10: I/O errors" after upgrading to Snow Leopard

Here's my situation: I recently upgraded my iMac (2.93 Ghz Intel Core Duo, 4GB of ram, model id is 9.1) from Leopard to Snow Leopard. I did a basic install (not a clean install), the installation went smoothly, no errors were reported and in less than 40 minutes I was up running Snow Leopard.


But... immediately, on the first launch, after a couple of minutes my Mac started beachballing, leaving it completely unresponsive for like 5 minutes. Afterwards, the spinning pinwheel disappears, my Mac continues running normally, and I don't experience much issues. At first I thought it was a one time thing, probably saving some settings up after the first launch, but... it has been happening every time I start my computer! Every time, it starts up, all my startup programs launch, the desktop icons appear, and then suddenly after a couple of minutes it starts beachballing again.


I now start to suspect there's something wrong. I launch the Console and take a look at the logs. There at the exact same time the beachballing occurs, i find like 3 or 4 subsequent "disk0s10: I/O errors". Now I'm starting to think it's a hard disk issue, so I bring up Disk Utility and check the S.M.A.R.T., it says everything is OK. I verify the disk, and it says everything is OK. Now I don't know what to suspect.


Something tells me it's not the hard disk failing (maybe it's denial), because the problem started happening immediately after installing Snow Leopard. With Leopard I didn't have any problems at all. Also, once the beachballing stops, my computer runs smooth and fast, much faster than with Leopard; and it seems the beachballing and the errors don't happen again until the next restart (though I haven't yet used it for a long period of time since this problem happened like three days ago). Another thing is that I recently transfered like 30GBs worth of files and I didn't receive a single error. Everything seems (as for now) to run perfectly well after the initial beachballing occurs.


So, I'm now facing two options: (1) Make a clean install and see if the problem persists, or (2) Replace the hard disk.


As all of you know, both options are pretty time consuming and annoying, so I really want to troubleshoot everything I can to see if the problem has a simpler solution. What other things can I check? Have any of you had this problem before?


Sorry to make my post so long but I believe the more information you get first hand the better, right? Please, I will really appreciate any advice.

iMac, Mac OS X (10.6.7)

Posted on Jun 17, 2011 1:23 PM

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Posted on Jun 17, 2011 1:33 PM

Have you tried booting into Safe Mode? Give that a try and see what happens. Watch for the same console errors as before.


I would also suggest downloading AppleJack - MacUpdate or CNET Downloads - and installing it then running it per instructions in its documentation.


Now, you mentioned console errors referring to disk0s10. Do you have multiple partitions on this drive or have you had them in the past? You can open the Terminal in your Utilities folder and at the prompt enter:


df


Press RETURN. I would be curious to see what's reported. Also, what is listed in Disk Utilities' sidebar? I would also like to know what if any process is associated with the disk0s10 error messages.


Last for now:


Open Activity Monitor in the Utilities folder. Select All Processes from the Processes dropdown menu. Click twice on the CPU% column header to display in descending order. If you find a process using a large amount of CPU time, then select the process and click on the Quit icon in the toolbar. Click on the Force Quit button to kill the process. See if that helps. Be sure to note the name of the runaway process so you can track down the cause of the problem.

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Jun 17, 2011 1:33 PM in response to yadielar

Have you tried booting into Safe Mode? Give that a try and see what happens. Watch for the same console errors as before.


I would also suggest downloading AppleJack - MacUpdate or CNET Downloads - and installing it then running it per instructions in its documentation.


Now, you mentioned console errors referring to disk0s10. Do you have multiple partitions on this drive or have you had them in the past? You can open the Terminal in your Utilities folder and at the prompt enter:


df


Press RETURN. I would be curious to see what's reported. Also, what is listed in Disk Utilities' sidebar? I would also like to know what if any process is associated with the disk0s10 error messages.


Last for now:


Open Activity Monitor in the Utilities folder. Select All Processes from the Processes dropdown menu. Click twice on the CPU% column header to display in descending order. If you find a process using a large amount of CPU time, then select the process and click on the Quit icon in the toolbar. Click on the Force Quit button to kill the process. See if that helps. Be sure to note the name of the runaway process so you can track down the cause of the problem.

Jun 17, 2011 1:59 PM in response to Kappy

Thank you for the fast reply! Right now I'm at the office so I can't do everything you suggested but I will do it as soon as I get home (didn't thought I'd get a reply this fast 😉).


As for the console errors, sorry I made a mistake. I recall it's really referring to disk0s1. Looks like I typed an extra 0 by mistake. I only have two partitions, one for Mac OS X and another for Windows XP.


As for the process associated with the disk0s1 error messages, I recall it saying something about "kernel".


I did check the Activity Monitor for processes hogging CPU% (I made it start at login and show the graphs in the dock just in case I couldn't move any windows). I never found any process using a large amount of CPU time. I didn't even noticed any spike on the graphs.


As soon as I get home I'll try your suggestions and I'll also verify that what I've told you is correct.


I was wondering, have you ever seen any cases where these "disk0s1: I/O errors" we'ren't necesarily due to a hard drive failure?

Jun 17, 2011 2:07 PM in response to yadielar

I/O errors may be indicative of hard drive failure or potential failure, but they may also simply mean the drive is corrupted.


Now that I'm clear about the typo you can forget the little Terminal exercise. But I would suggest doing this:


Repair the Hard Drive


Boot from your Snow Leopard Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported, then quit DU and return to the installer.


If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.

If there is a just corruption this may either fix it or point out what it is and if it's otherwise fixable. At best you may only need to reformat the drive or use Disk Warrior to repair a corrupted directory.

Jun 17, 2011 2:25 PM in response to Kappy

Good. So I have three things I can try when I get home, right?


  1. Boot in Safe Mode and watch for the same console errors.
  2. Download and run AppleJack.
  3. Boot from the Snow Leopard Installer disc, run Disk Utility and follow your instructions.


Or is anyone of these redundant? Just checking.


As for booting from the Snow Leopard Installer disc and running Disk Utility, my iMac shipped with Mac OS X 10.5 and I recently purchased the Snow Leopard disk. There shouldn't be any problem with doing option #3 with that disc, right? It's just that I've heard there are some utilities that are only available in the CD that came packaged with your Mac.


Thank you so much again for your help.

Jun 19, 2011 2:35 AM in response to yadielar

OK. Here's what I found out.


When I boot in Safe Mode the problem does not occur (and I discovered why, I'll explain further along). Also, Disk Utility didn't report any errors in either the "Macintosh HD" volume nor the "WINDOWS" volume.


Looking closer at the console errors I noticed a couple of things. Here are the console errors:


6/19/11 4:03:02 AM kernel disk0s1: I/O error.

6/19/11 4:03:02 AM kernel

6/19/11 4:03:02 AM kernel

6/19/11 4:04:09 AM kernel disk0s1: I/O error.

6/19/11 4:04:09 AM kernel

6/19/11 4:04:09 AM kernel

6/19/11 4:05:17 AM kernel disk0s1: I/O error.

6/19/11 4:05:17 AM kernel

6/19/11 4:05:17 AM kernel

6/19/11 4:05:17 AM firmwaresyncd[63] /sbin/mount exited with 71

6/19/11 4:05:17 AM firmwaresyncd[63] Command /sbin/mount output: mount_msdos: /dev/disk0s1 on /Volumes/firmwaresyncd.QsGgXz: Input/output error


First of all, the error is reported on disk0s1. So I ran diskutil list on Terminal to check which drive was this. These are the drives and partitions that were listed:


/dev/disk0

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *640.1 GB disk0

1: EFI 209.7 MB disk0s1

2: Apple_HFS Macintosh HD 605.5 GB disk0s2

3: Microsoft Basic Data WINDOWS 34.3 GB disk0s3


As you can see, disk0s1 is the EFI System Partition (ESP) in my Mac. After a little research I found out that this partition is used as a stage for handling firmware updates. I also found out that this partition is not really needed to run Mac OS X. This explains the subsequent appearance of the firmwaresyncd command which, according to the Apple's developer manuals, runs at boot time to synchronize the firmware files from the root filesystem to the EFI System Partition (ESP). Also, it does not run when the system is performing a Safe Boot.


Now this explains why the problem only happens after I boot and never happens again until I reboot. It also explains why it doesn't happen when I run in Safe Mode.


Therefore, the problem I'm experiencing is basically the following:


  1. At boot time the firmwaresyncd command tries to access the EFI partition to synchronize the firmware files from the root filesystem to the EFI System Partition.
  2. It seems that the EFI partition at disk0s1 is either corrupted or inaccesible so the firmwaresyncd command can't access the partition and after a couple of tries throws the input / output error.


Now the next thing I did was to run Single User Mode and run fsck_msdos /dev/disk0s1 to see if I could repair this partition. Unfortunately, I got the following error:


:/ root# fsck_msdos /dev/disk0s1

** /dev/disk0s1

** Phase 1 - Preparing FAT

** Phase 2 - Checking Directories

** Phase 3 - Checking for Orphan Clusters

disk0s1: I/O error.

0 [Level 3][ReadUID 0] [Facility com.apple.system.fs] [ErrType IO] [ErrNo 5] [IOType Read] [PBlkNum 1744] [FSLogMsgID 1787532898] [FSLogMsgOrder First]

0 [Level 3][ReadUID 0] [Facility com.apple.system.fs] [DevNode devfs] [MountPt /dev] [Path /dev/disk0s1] [FSLogMsgID 1787532898] [FSLogMsgOrder Last]

disk0s1: I/O error.

0 [Level 3][ReadUID 0] [Facility com.apple.system.fs] [ErrType IO] [ErrNo 5] [IOType Read] [PBlkNum 1744] [FSLogMsgID 1585536958] [FSLogMsgOrder First]

0 [Level 3][ReadUID 0] [Facility com.apple.system.fs] [DevNode devfs] [MountPt /dev] [Path /dev/disk0s1] [FSLogMsgID 1585536958] [FSLogMsgOrder Last]

Unable to read FAT (Input/output error)

Free space in FSInfo block (364217) not correct (173941)

Fix? [yn] y

6 files, 86970 KiB free (173941 clusters)


So that's what I've found out for now. 😟


What do you think I should do now? Should I try to erase and re-partition the disk to see if it solves the issue? Could these errors suggest the disk is about to fail?


I could technically keep using the Mac like this since the EFI partition isn't strictly needed to run Mac OS X and this problem only happens once at boot time (and I do keep a Time Machine backup). But should I?


Any thoughts?

Jun 19, 2011 12:32 PM in response to yadielar

If you feel comfortable with this here's a method for erasing the EFI partition:


Removing or Reformatting the EFI Partition


1. Open Terminal application in the Utilities folder.


2. At the prompt enter: sudo -s (and type in your password)


3. Next enter: diskutil info / | grep Identifier - this tells you the values for diskXsY for '/', which is the currently-booted system. (If you're doing this on a disk other than the one you've booted from, you need to modify accordingly.)


4. Then enter: diskutil list - diskXs1 should be called EFI. this is the hidden EFI partition on your target drive.


5. Lastly enter: diskutil eraseVolume "HFS+" "EFI" /dev/diskXs1 - now, be *VERY* sure this is the correct drive. this will format the EFI partition as HFS+. (NB After erasing it will try to mount it, but will fail with "Could not mount disk0s1 with name after erase". Ignore this).


For your situation substitute disk0s1 in the above commands.

Jun 19, 2011 7:57 PM in response to Kappy

OK. Just to be sure (I'm not that comfortable using Terminal but I can manage).


I must do these commands as follows:


sudo -s (and type my pasword)

diskutil info / | grep Identifier (to make sure which is the disk for the currently-booted system)

diskutil list (to check which disk is the EFI partition)

diskutil eraseVolume "HFS+" "EFI" /dev/disk0s1 (to format the partition as HFS+ assuming disk0s1 is EFI)


So basically your suggesting me to erase the EFI partition and format it as HFS+. And I can do all this from Mac OS X without any problems, right?

In the last command, the "EFI" part, what does it do? I really don't understand well what's in the EFI partition exactly. Are there some kind of files or something? Would I have to do something later to write them back or the "EFI" part of the command takes care of it?


Sorry to ask you so many questions, I just want to make sure formatting the partition is totally safe.


Thanks for your help so far.

Jun 19, 2011 8:22 PM in response to Linc Davis

Hi Linc, thanks for your help.


Are you suggesting I do this if formatting the partition doesn't work?


I suppose repartioning the drive would be the last definitive option since it will wipe everything out and restructure the disk from scratch. If I get errors trying to repartition the drive, that would mean it's a hardware problem, right? Should I try to zero the drive? I've heard it helps to quarantine bad sectors.


What do you think?

Jun 19, 2011 8:41 PM in response to yadielar

Formatting the EFI partition will make the volume unbootable. If that's not what you want, back up and repartition. As for zeroing the drive, I don't think that's necessary. If there are bad sectors, the next time you try to write to them (if you ever do), they'll be mapped. Bad sectors are only a problem if they go bad after you've written to them.

Jun 19, 2011 11:28 PM in response to Kappy

Thanks Kappy!


I successfully formatted the partition. It didn't even seem to have any problems whatsoever. It was pretty fast. Here's what the Terminal said:


bash-3.2# diskutil eraseVolume "HFS+" "EFI" /dev/disk0s1

Started erase on disk0s1

Unmounting disk

Erasing

Initialized /dev/rdisk0s1 as a 200 MB HFS Plus volume

Mounting disk

Finished erase on disk0s1 EFI


I rebooted and crossed my fingers. It booted fine and the beachballing nor the errors are nowhere to be found. 😀


One thing that bothers me though is that the EFI partition now appears beneath Devices in Finder and I'm pretty sure it's supposed to be hidden. Is there a way to make it hidden (perhaps through Terminal) like it originally was?


I also hope I can do firmware updates successfully. I supposse I'll find out in the future.


If you could give me your advice one last time about hidding the EFI partition I will really appreciate it! You've been so helpful, you have no idea how thankful I am!

Beachballing and "disk0s10: I/O errors" after upgrading to Snow Leopard

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