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Although everything is working fine with my Macbook Air from Mid-2013, I have a few errors that bother me.

Here they are:

Onyx says this:

The SMART status was not verified because it is not supported by this hard disk.

But the system report writes this:

disk0s2:
  Media Name:   APPLE SSD SD0256F Media
  Size: 250,14 GB (250 140 434 432 bytes)
  Medium Type:  SSD
  Protocol: PCI
  Internal: Yes
  Partition Map Type:   GPT (GUID Partition Table)
  Status:   Online
  S.M.A.R.T. Status:    Verified
  PV UUID:  4F6EBACC-CA60-4DE6-95BF-37F42D820284

After installing smartmontools:

smartctl disk1 -a  
SMART support is: Available - device has SMART capability. 
SMART support is: Enabled  
=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED 

So SMART seems good, maybe onyx is in fault. But my cksum mismatch problem is still here

When I run disk utility and I perform a verification on my hard drive I always get this:

Invalid Disk Label @ 250123653120: cksum mismatch

And sometimes if I wait enough time (a few days) after a repair (with the cmd+R on boot utility) I get this kind of error: Incorrect block count for file (...)

This last problem seems to happen with files I downloaded and most likely which I didn't finish to download.

What I think:
When Yosemite came out I installed it, but since I found that even resizing a window wasn't as smooth as on Mavericks I decided to downgrade using my Time Machine backup.

Do you think upgrading back to Yosemite would fix all this? And would I still find this kind of performance?

Edit: If it is a good idea, I have no problem with doing a clean install of Yosemite.

Thanks in advance for your help. My Mac is still young and I don't want him to be sick.

  • Please try to install smartmontools and report back – klanomath Mar 6 '15 at 9:59
  • Here is a part of the result of smartctl disk1 -a SMART support is: Available - device has SMART capability. SMART support is: Enabled === START OF READ SMART DATA SECTION === SMART overall-health self-assessment test result: PASSED So SMART seems good, maybe onyx is in fault. But my cksum mismatch problem is still here. – Paul V Mar 6 '15 at 12:48
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DiskWarrior is brilliant at repairing file system issues that Disk Utility can't manage, but if you're not bothered about repairing your existing file system then you may as well wipe and restore.

In addition the above answer I'd strongly recommend creating a USB installer so you can boot from that and then properly repartition and reformat your SSD. Installing from USB will be much quicker than performing Internet Recovery, and you definitely don't want to restore from the recovery partition if there is any doubt about the file system integrity.

To do this...

Download the 10.9/10.10 installer from Apple. Do not run the installer, cancel it. Next, build a USB installer from the installer so you can perform a completely clean install. Take an 8GB USB stick and (very important) name it Untitled. Then run this command in Terminal, changing both instances of Yosemite to Mavericks if required...

sudo /Applications/"Install OS X Yosemite.app"/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/"Install OS X Yosemite.app" --nointeraction

It will take a few minutes to process so be patient.

Then when you're ready to install, start the machine and hold alt/option to bring up the boot selector, and then select the USB installer you just created.

Remember to run Disk Utility before commencing the actual installation!

  • I will find a usb key and try this. I keep this thread updated. – Paul V Mar 6 '15 at 12:22
  • Problem solved with a clean install of Yosemite. Performance seems okay. Thank you. – Paul V Mar 7 '15 at 11:35
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You file system is corrupted, hardware is probably fine. Backup, wipe and restore.

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