I am getting (seemingly random) disk I/O errors on my bootdrive. At first I thought it was caused by a faulty hard drive, but now I've replaced it and I still get those errors.

These are the steps I have followed beginning from the first time I noticed something was wrong:

  1. Laptop hangs with just Google Chrome and Postbox (an e-mail application)
  2. I restart the laptop, but it never gets past the screen with the grey apple.
  3. Started Apple Hardware Test by holding "D" during startup. This came up with no errors
  4. Through Verbose mode, and Disk Utility of the install CD I saw that it had disk I/O errors.
  5. I switched the Momentus XT drive for the stock Apple HDD.
  6. Installed a fresh copy of Snow Leopard
  7. Recovered everything from a Time Machine backup

After a day it started giving disk I/O errors again in Console. This makes me think that an app or a setting is causing this as it is unlikely that both the hard drives are corrupted.

How can I pinpoint which application is the cause?

Below are my system details:

MacBook Pro 5,3
2.66 Ghz / 8GB RAM
Snow Leopard 10.6.8
First HDD: Seagate Momentus XT 500GB
Second HDD: Stock Apple Hitachi 320GB
  • If you are not equipped like a repair shop with ample spares and ability to isolate failures by systematically testing each component in the chain, I would re-seat the cables (or the drive if you are not comfortable getting to the cable interface to the logic board). IO errors are almost always a failing drive so swapping that drive once the error rate (or loss of time or data) outweighs the cost of the time and parts to repair that drive.
    – bmike
    Jan 7, 2013 at 16:00
  • 1
    If it's not the harddrive it can very likely be the the internal SATA cable the drive is connected with.
    – MacLemon
    Jan 7, 2013 at 23:03
  • @MacLemon Is there a way to test this with my current setup? I am now running Snow Leopard from the Momentus XT in an external enclosure through Firewire. No problems (yet). Jan 7, 2013 at 23:07
  • Replace the cable for a known-good cable and see if the problem goes away. If you don't have any troubles with the same disk in an external enclosure my bet stays on the SATA cable.
    – MacLemon
    Jan 7, 2013 at 23:10

1 Answer 1


I've had my MacBook Pro repaired. They changed the SATA cable, and everything is working again.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .