Yosemite: boot hangs at 50% percent

Think you've got a different problem there AquinasHub. disk0s2: I/O error almost always means your disk is done for.

AquinasHub wrote:

disk0s2: I/O error.

It might be a malfunctioning HDD.

I'd love to get into a disk repair mode or would be able to boot with the "c" command into an OS X boot USB stick or see a log file, but I'm not even able to get there because of the stuck loading bar. For the record: Of course I tried reseting PRAM and SMC. Makes no difference. I begin thinking this might be a hardware or firmware issue.

Your drive is bad, that's what I/O Error means. It is most likely a bad blocks failure, which is very common, and progressive – the more you use the drive, the worse it tends to get. Best to deal with it pronto.

Thanks guys! I'm positive the disk is done for.

Therefore if anyone my kind of boot error, try accessing verbose-mode on startup by holding Cmd+V and look for anything hard disk related (MANY i/o or mounting errors). That's when you might need to replace your hard disk.

AquinasHub wrote:

Thanks guys! I'm positive the disk is done for.

Therefore if anyone my kind of boot error, try accessing verbose-mode on startup by holding Cmd+V and look for anything hard disk related (MANY i/o or mounting errors). That's when you might need to replace your hard disk.

There are better ways to monitor the hardware health of your drive. My personal favorite is SMART Utility from volitans-software.com.

I found this thread on JAMF's discussion boards to be helpful too... https://jamfnation.jamfsoftware.com/discussion.html?id=12589

Hello again everyone,

im typing from my phone once again as after 3 weeks of smooth sailing (after restoring Yosemite from a time machine backup for the 10th time) finally my machine has started to hang again. I did some more searching as to the cause of this problem because I am just a human and not an robot or computer genius, I need it dumbed down for me. Nonetheless I was able to find that in "console" which is a utility under applications I was able to see (in between periods of the spinning pinwheel of death) that there were a few I/o errors. This I had not previously thought to be an issue, as in I had no idea there were I/o errors going on which apparently means that the disk is on the way out...

well this is all very interesting and is love to post a log report however at this point things just freeze up pretty good and I can't ever being up a system report without hanging the machine so.......

im confused as my machine worked flawlessly on Mavericks and ever version before that but from the first **** day I loaded Yosemite things acted funny and hang at boot which NEVER happened before and now I have I/o disk errors!! So way to go apple for releasing Yosemite the disk killer. My macs only four years old and I know some discs just go but come on... It worked perfectly before you dropped it off a cliff with this pos Yosemite bs.

at this point in the game I'll need to buy a new disk and keep you guys posted on if this problem happens again. I'm thinking I'll get as new a disk as possible that way if Yosemite kills this new disk I'll know apple truly has seriously disapointed and cost me even more money on this bs release. I'm not usually one to jump to conclusions but its too coincidental that I've had this issue and all the other people here have had the same things happening to theirs.

Come on apple get your **** together.

signed,

everyone!

Amerika X wrote:

im confused as my machine worked flawlessly on Mavericks and ever version before that but from the first **** day I loaded Yosemite things acted funny and hang at boot which NEVER happened before and now I have I/o disk errors!! So way to go apple for releasing Yosemite the disk killer. My macs only four years old and I know some discs just go but come on... It worked perfectly before you dropped it off a cliff with this pos Yosemite bs.

at this point in the game I'll need to buy a new disk and keep you guys posted on if this problem happens again. I'm thinking I'll get as new a disk as possible that way if Yosemite kills this new disk I'll know apple truly has seriously disapointed and cost me even more money on this bs release. I'm not usually one to jump to conclusions but its too coincidental that I've had this issue and all the other people here have had the same things happening to theirs.

Come on apple get your **** together.

Sorry, Yosemite is not a "disk killer."

Your experience is not unusual at all. We see it a lot. Your disk was starting to have a bad blocks failure, which is usually a progressive condition. The more the disk is used, the worse it gets. Installing a new operating system is a very disk-intensive process. It's very common for something like this to push an iffy disk over the edge.

All hard drives fail. The peak of the bell curve, the most common age of failure, is about three years. As a Mac consultant, a bad blocks failure is the most common type of failure I see. Periodic SPODs (Spinning Pizzas Of Death) is the common symptom of a bad blocks failure. You can also often find I/O errors in the logs. You can use a utility like SMART Utility to access the built-in self-monitoring circuitry of a drive, and I've only seen two or three drives in 15 years that had to be failing despite SMART attributes being okay.

I was also initially motivated to reply about the irrelevance of all these disk I/O errors on a thread about Yosemite boot up issues. However, I then began to consider that actually with the Yosemite boot up problems comes an awful lot of forced power off and power ons which in my experience is a sure fire way to introduce problems to a disk if done repeatedly. I think it's possible that there is a link in some instances. Having said that, it would be good if this thread were to return to addressing the key issue of the failed boot situation with Yosemite installations.

ITPaolo wrote

I was also initially motivated to reply about the irrelevance of all these disk I/O errors on a thread about Yosemite boot up issues. However, I then began to consider that actually with the Yosemite boot up problems comes an awful lot of forced power off and power ons which in my experience is a sure fire way to introduce problems to a disk if done repeatedly. I think it's possible that there is a link in some instances. Having said that, it would be good if this thread were to return to addressing the key issue of the failed boot situation with Yosemite installations.

I disagree on two counts. First, there are multiple possible causes for the 50% boots. As I wrote elsewhere in this thread, in one client's it was due to a failing graphics card. And the person with the I/O errors, well a failing disk could very likely be the cause of the incomplete booting.

Second disagreement, I don't think the power off and power onsw have anything to do with making a disk fail. In the old days, that may have been the case. But not anymore. I have seen many many instances of a disk being pushed over the edge by an operating system update; many similar reports on MacInTouch.com.

cavenewt wrote:

ITPaolo wrote

I was also initially motivated to reply about the irrelevance of all these disk I/O errors on a thread about Yosemite boot up issues. However, I then began to consider that actually with the Yosemite boot up problems comes an awful lot of forced power off and power ons which in my experience is a sure fire way to introduce problems to a disk if done repeatedly. I think it's possible that there is a link in some instances. Having said that, it would be good if this thread were to return to addressing the key issue of the failed boot situation with Yosemite installations.

I disagree on two counts. First, there are multiple possible causes for the 50% boots. As I wrote elsewhere in this thread, in one client's it was due to a failing graphics card. And the person with the I/O errors, well a failing disk could very likely be the cause of the incomplete booting.

Second disagreement, I don't think the power off and power onsw have anything to do with making a disk fail. In the old days, that may have been the case. But not anymore. I have seen many many instances of a disk being pushed over the edge by an operating system update; many similar reports on MacInTouch.com.

On the first point, I'm only saying the I/O errors are potentially irrelevant here because there is a clear distinction between a failing disk causing a problem (which would be a problem regardless of the OS) from the other curious things that have been noted in this thread. The new issues that seem to have arrived with Yosemite are the ones that I think need to be examined more closely here, rather than generic problems that apply in any situation. The handling of Kernel Extensions for example seems to be causing some interesting problems and some people seem to think there are difficulties with Active Directory. However, that is a selfish view point because there are of course plenty who won't make the distinction between these types of problems.

On your second point, I would challenge that if, as you say, simply installing an OS is enough to push a disk over the edge then is it not feasible that forcibly shutting off the power to that same active spinning disk dozens of times in a row could have a similar effect. I don't know for sure but my personal speculation is that it might.

Ok. I ordered a new SATA Drive for my mac which will be here next week. I'm pretty confident that once it comes I'll install it, restore from time machine back up and everything will work as expected. Stable and cool. If the average life expectancy of these drives really is 3 years then I guess I was due for one anyway so calling Yosemite a disc killer may have been extreme. However I too had to do a LOT of hard resetting right after first installing yosemite and I never had to do that before so perhaps the Yosemite OS is overly intense for hard drives on installs and then caused some bad sectors (or made some worse) then with the hard shut downs things could have just gone from bad to worse.

What is strange is that after a few weeks of just barely getting my machine to even turn on, I was finally able to do a time machine restore from back up that actually worked! As in (like I've said above) my machine ran just fine with Yosemite for over 3 weeks!!! Then as I said problems persisted and I noticed a LOT of I/O error messages in the log and of course the pinwheel freezes got worse than ever.

Whats even more strange is that I repaired permissions and repaired disc last night and did what I thought might be my last back up and now everything is smooth! No spinning pinwheel for the past 14 hours!

So, this is strange but to be honest the I/O error thing really does have me thinking my disc was just **** so well see on tuesday after I do a full re-install.

Thanks for the help.

I had that happen yesterday too. Resetting did nothing. Finally after like 10 tries of rebooting, it went.

I have my own MacBook Pro that is NOT on AD doing this as well as a LAB of about 34 brand new iMac's on 10.10 doing this. About half of them will not boot, all of them are on AD though.

I work in a Mac lab as well and it's still happening pretty consistently on our newer iMac and two old Mac Pros. Haven't had it happen a single time on our 2014 mac pros or oddly enough, our 2011 iMac.

Really wish this would get fixed soon. It's very annoying to deal with in a lab setting. Just so happens that our iMac is the most used machine we have.

Safe Mode, Resetting PRAM, or fixing Disk Permissions does not fix the issue.

Here are 2 steps to resolve:

1. From the recovery partition (or target-disk or single-user mode, if you don’t have a firmware password,) deleting the following directories has sometimes been enough:

rm -rf /Volumes/Macintosh\ HD/private/var/db/BootCache*

rm -rf /Volumes/Macintosh\ HD/Library/Caches/com.apple*

If you have FV - Remember to unlock the drive with Disk Utility if it’s FV2-encrypted, the commands assume you’re running Terminal from the Utilities menu in the recovery partition, remember to change “Macintosh HD” to your drive label accordingly.

2. You may also need to adjust this preference by defaults write, along with one more reboot:

defaults write /Volumes/Macintosh\ HD/Library/Preferences/com.apple.loginwindow.plist DSBindTimeout -int 10

(Make sure the above is all one line.)

The above preference change overrides what is supposed to be the default value, 60 seconds, but alter if you think latency to getting a response from your DC(‘s) may be longer. As you may have experienced, waiting 60 seconds does not actually make a difference, so it’s a possibility that this code path just isn’t being followed properly. 10.10.2 Betas doesn't seem to fix this as of yet.

Hope this resolves all your issues.

FOUND THE ANSWER!

Decided to upgrade to Yosemite yesterday evening, not sure what happened but my macbook lost power suddenly. Restarted it only to find that i was stuck at the 50% of death screen. After countless reboots, resetting the PRAM, repairing the hard drive several times and several different command + key gestures i was ready to throw it out and finally upgrade to a new macbook (using a late 2010 model unibody). Decided to try one more thing! Booted into Recovery mode i believe it was? ( 4 options - backup from time machine, install mac OS X, disk utility and another i can't remember for the life of me)

I chose the install OS X option, had to re-connect to wifi and re-download OS X yosemite 10.10 from the App Store, 45 minutes later i am up and running and able to post this.

TL;DR - Reinstall osx Yosemite. Problem solved!