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I have an image in a folder on my Macbook that is used to store files for rotation as my background. The folder contains about 20 photos, and I haven't moved or modified the folder in nearly a year.

Today, one of the images started to show a bit of artifacting that one would typically see if the file had been corrupted. What might cause something like this to happen?

Additional Information

In full disclosure, let me give a bit of background. About a week ago, I was walking to my car, from my office, in the light rain. A quarter of the way to my car, (which was located in the far end of the lot) the rain started to seriously pour and it was hailing as well.

So, I sprinted to my car. While running, my laptop bag unzipped itself in the process, my Macbook fell out of the bag, bounced, rolled 3 times across the pavement and landed in a about 1 inch of water-- I was sure it was dead.

However, I blasted the car heat on it on the ride home and when I got home, the machine booted it (What?!) and it has worked perfectly for the past week.

So far, I've experienced no form of discernible hardware failure and this is the first glitchy thing I've seen since last Friday, and I use this machine every single day.

Is this file corruption almost certainly a sign of hardware failure or is there a reasonable chance that this file could have been corrupted by some other reason and it was just by chance of circumstance that the file was corrupted shortly after I dropped my Macbook?

I have AppleCare on this device, but I doubt they will help me fix it unless I can point to a specific problem.

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Do you have a normal hard drive or an SSD? Was the Mac sleeping or turned off when it fell? – slhck Jul 20 '12 at 16:05
It was in a sleep state (since it was closed) and, yes, I have an SSD. I forgot to mention that. – RLH Jul 20 '12 at 16:11
If it’s only one of the photos, then it’s probably just a bad sector from the fall or even maybe even just incidental. – Synetech Jul 20 '12 at 16:37
Well, the odd thing is the sector has worked fine for a week. These images change out pretty frequently (I also have a thunderbolt display), so I see the same image at least twice a day. When it showed up as my background this morning, I saw the artifacting, but not before. – RLH Jul 20 '12 at 16:42
The fact that you only created & wrote these files once and didn't write to these files again is not pertinent when you use a SSD. Solid state drives use wear leveling techniques to maintain uniform usage of all sectors. So files the you created a while ago (and never changed) will still be moved around the SSD without your knowledge. If the data from these sectors were not moved periodically, then these sectors would be under-used in terms of erasures and writes. Also note that NAND flash has a potential fault called "read disturb". – sawdust Jul 20 '12 at 23:46
up vote 2 down vote accepted

There are many possible answers to why a file suddenly went corrupt. Since you recently had phisical damage happen to the system that is the most likely.

I would suggest backing the pc up now. Since the pc was dropped in to water you could have falling damage to the HDD, bad sectors or something not in alignment any more.

you could also have contaminate damage from the water. there is a lot of junk in water just like how you get a coating of sand and salt at the beach the same can easily happen to your pc when it gets wet. some of those bits and pieces may be conductive and can cause arcing or could chemically react to parts in the system.

beyond the fall considering there was a storm, It may also be that there were power fluctuation that you could not see. if a power fluctuation is timed just right while a drive is trying to do something it may affect near by data. the electronics for these systems have been built to expect less then perfect power, even then during storms or if the electric company has to do work near by you never know how good the power going to your system is W/O putting a meter on it and watching it.

As for drying the pc you did pretty good by just using your car heater. consider the electronics needs to be similer to a persons. you don't want it to get warmer then about 90-100 F if you would get burned by it blowing on you all day so would your pc.

Evaperation is the only way to let it dry out and will often take a day or 2 to completely dry. if you cook the laptop you may melt parts there are many plastic membranes used like in the keyboard that are very thin and easy to destroy with fast drying through high heat.

As for next steps after backing up the pc there should be some sort of drive tests available to you. smart diagnostics built in to the HDD are handy but not an end all to drive health. the drive should have a non destructive read and possibly write test done to the surface to verify you have no bad sectors. I know of plenty for Linux and pc but none for MAC.

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I will be getting my MAC cert in the near future so have never needed a such utilities. I'm sure there are plenty out there that work great I just don't have a clue what they would be. – Kendrick Jul 20 '12 at 16:33
Thanks for the additional information. I did run a disk verification, and it checked out. The odd thing is that this file wasn't corrupt until today. Everything has been working fine until now. Also, I have an SSD, not a HDD. Should that make any difference? Is there a chance that the SSD is sealed better? – RLH Jul 20 '12 at 16:41
SDD is entirely different technology depending on the type is is less sealed, how ever it wont have falling damage like a hdd could. more prone to getting electrical damage. – Kendrick Jul 20 '12 at 16:47
Yes, I am aware of how they operate. I'm honestly not sure much water got into the system (miraculously). It sat in the puddle for no more than 5 seconds, and I didn't feel any water moving back and forth, nor did anything drain out of it. Still, it took a nasty fall and has quite a gash in the aluminum. – RLH Jul 20 '12 at 16:49
It is far more likely its electrical damage if it is such. the "fun" part about zaps is it may take years for a minuet zap to cause failure. this may have been the straw that broke the camels back on a manufacture defect or just bad timing. – Kendrick Jul 20 '12 at 17:00

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