Macbook pro mid-2012 13" has very slow disk access

Question

Until 3 days ago my macbook pro mid-2012 13" running OX 10.8.3 was running fine. Then, it showed very slow response anytime it had to access the hard disk. After doing the usual checks and disk first aid repairs to no avail, I booted from my external disk with an older copy of my hard disk and everything then worked as normal, except when I accessed the internal hard disk, then it crawled once again (spinning beach ball, took many seconds just to open a finder window and then several minutes to display the contents). I ran the Apple Hardware Tests and it said everything was fine, even though it tooks several minutes before the test would actually start. I also ran the program BlackMagic Speed Disk to find out if the disk was having transfer speed problems and it showed a respectible transfer rate (60MB/s), not great but not like the 0.3MB/s I was getting when I tried to back up the internal disk. I was using Carbon Copy Cloner to try to back up the internal disk but had to give up since at 0.3MB/s, it would take days to back up the 250GB on the disk. I found on the web that using "restore" in Disk Utility, I could do a disk copy without the file by file copy which allowed me to back up my disk in "only" 6 hours. Booting from my newly made copy on an external disk worked fine and ran at nearly normal speed (slightly slower since it was an external disk running through USB2). As a final attempt to prove this was a disk problem, I erased the internal disk and reinstalled OSX 10.8. I am still waiting for this install to finish, it has been 5 hours although the progress bar said it should be done in 20 minutes. This was fairly convincing evidence that it is not a software or settings problem. However, all my web searches could find no other case of a problem like mine. I presume I have a failed hard disk but as all the diagnostic programs say it is working fine, I was hesitating to bring it in without hard diagnostic evidence. If anyone knows what might be the problem, it would be much appreciated to hear from you.       

Answer 1

It should not take 5 hours to install Mac OS X.  There is something wrong with the disk.  Try reformatting where you do a wipe of the drive (an select the option to write zeros which will remap bad sectors).   Then try to install MAc OS X.
I got this information from here:
http://reviews.cnet.com/8301-13727_7-20064489-263.html
Back up your data.
Use Time Machine or a system cloning utility to create a full and restorable backup of your data. If you suspect bad blocks, then when cloning you might consider not using a "block-level" copy process, since this will likely run into problems.
Boot to the utilities DVD.
If you have a boot DVD for a tool like Drive Genius or another drive utility, then boot to that; if not, use your OS X installation DVD (once you select your language, open Disk Utility from the Utilities menu).
Format the drive.
Using your selected utility, format the drive and check for bad blocks. If you are using Disk Utility, click the Erase tab, click the Options button, and then select the option to write zeros to the disk (you do not need to do multipass erase options, as this will provide no additional benefit for managing bad blocks). Writing to zeros may take a couple of hours depending on the size of the drive, but when done the drive will have remapped any blocks that were not reliably read.
Restore the OS installation.
If you have used Time Machine to create your backup, boot to your OS X installation DVD (if you are not using Disk Utility) and use the option in the Utilities menu to restore from backup. Attach your Time Machine drive and then proceed with the restoration, selecting the newest backup as the one to restore to your system. If you have used a system cloning tool, then attach the cloned drive and boot off of it (hold the Option key at start-up to select it from the boot menu). When you are booted to the cloned drive, run your cloning utility to copy the installation back to the computer's main boot drive.An optional approach here is to perform a full reinstallation of the OS from your installation DVD, and then migrate your data, applications, and settings from either the clone or the Time Machine backups using Apple's Migration Assistant.