What happens at the Mac OS level when the SSD finally wears out?

Question

I have been reading up on SSD technology and don't know of any first hand reports on what happens when an SSD eventually fails due to over use. I am most interested in the SSD that apple includes as a factory option - but aftermarket information is certainly welcome.

• Does the available capacity the OS reports shrink as the SSD marks portions of the memory unreliable?

• Does an internal or external error rate climb and eventually trigger a SMART warning to the OS? (and can we peek at those recoverable error rates under the hood?)

• Does it just get slower and slower running garbage collection more and more often trying to find a place to store data as the flash storage system degrades?
• Practically is it possible to measure how much extra storage space remains to cover for failures and wear leveling? (assuming the SSD controller will pool memory and avoid bad/overused blocks before failure)

I am somewhat familiar with failure modes of hard drive storage but looking for similarities or differences between HDD and SSD. For example, the OS can detect (presumably using fsck and journaling) problems writing new data reliably to a HDD and warns you the drive is now mounted in read only mode. Tools like Drive Genius allow all sorts of testing specific to HDD but I'm unaware of tools that dig into SSD for whatever data may be available.

Are there similar precautions built into the Mac OS to handle eventual SSD failure modes or is this technology too new for this sort of pre-planning for when things eventually fail?

EDIT: Third party drives appear to slow down significantly as they approach the end of their service life. Some speed up substantially or totally with an erase. Still no answer on Apple Branded SSD.

Answer 1

"Does it just get slower and slower running garbage collection more and more often trying to find a place to store data as the flash storage system degrades?"

^^ This is what I've seen on two occasions (Aftermarkets tho, possibly the same in Apple drives).

They didn't entirely stop working because I eventually replaced them, since things become like a Windows XP after three years of use and no maintenance.

Another SSD I remember failing did it probably from day three, when it failed to mount on a few occasions. Then it failed to mount again later the same day until it eventually never mounted again. It was under warranty and I replaced it.

The SSDs I still have (non Apple) don't show signs of shrink, probably because the space you lose is not a lot compared to the size of the drive. I'm guessing that would be the case.

Although drives tend to live 2-3 years (SSDs), I'd say be prepared for a -possible- change after 1 year.

Answer 2

My aftermarket Intel SSD had a bad sector, which was reported by Disk Utility. From my understanding, the SSD will get slower and eventually have more bad sectors, which will be noticed if you do a Disk Utility scan.

Warnings because of SMART-data reporting more disk errors than acceptable aren't build into the OS, as far as I know. Disk Utility does show SMART errors, but not in much detail. Tools like SMARTReporter will give you warnings when your SSD is degrading.