I bought a new iMac with and internal SSD. How long under normal use (I am not a power user) should it last? I heard that the cells start to fail after a while.
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Time is hard to tell, they really just have a certain number of writes per sector or area and that amount of writes depends on the brand or generation as they are always getting better and lasting longer. You would have to look up data on the specific SSD that you have and find out what the write max is. Also, they use software that is supposed to move around the chips for writes and rewrites to try to keep an even amount of wear in each area. I’m no expert (other than working with them daily and what I have read) but that’s the way that I understand it anyone else feel free to jump in and correct me. 
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@JamesC_HTAssets is on the money, best bet is to look up manufacturer data on the model you have. They’ll publish MTBF (mean time before failure) specs that you can rely on for a general idea. Most SSDs will also output the amount life remaining as part of their S.M.A.R.T health data. I’m not sure how to check that data on OS X but I’m sure there are tools available if it isn’t built into the OS.
I’ll add a bit from personal experience - you don’t need to worry about wear any more than you would with a magnetic disk. Probably less so. Looking at the stats on a Kingston/HyperX NVMe disk that I installed 3 years ago, it reports 100% life remaining with 122TB of writes and 20TB of reads since manufacture date.
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I agree that you shouldn’t worry about it much, if your drive is going to fail by itself there isn’t much you can do about it but you would need to be a real power user to wear it out. I wouldn’t use an SSD in a system which is writing constantly e.g. CCTV.
The largest writes to my laptop SSD are probably when it sleep/hibernates and the contents of RAM are written to disk which could be up to 16Gb at a time
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The sophisticated wear leveling algorithms built-into the firmware of all SSDs protects individual cells from overuse. In my experience SSDs last at least as long as spinning drives. Early fears that they’d be fragile have proven unfounded.
Except for the price differential (which is rapidly shrinking) I can see no reason not to use SSDs. In fact, it’s all I buy.
@tokyotony Can I make this an “Ask the Tech Guy” episode?
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One suggestion I recommend for a more sophisticated user it to have more RAM in their system and then to use a RAM disk of some sort for files that change frequently but don’t really matter. In my case, I use the 4G of free Radeon RAM disk (link at bottom) and in there I store my browser cache and any downloads of files I am just going to install and then throw away (or relocate to a backup to keep.) And when I develop software for my own use or for others, I allow them to specify a location in the configuration of where to put throwaway temp files.
There is only one little caveat that I will warn extra power users about. If your RAM disk is really large (I use one of 16GB on my most powerful machine that does Handbrake transcodes) that Windows will get confused if your main drive is low on space and use the RAM disk for its temporary install files and then of course lose them all as soon as it reboots.
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Great. Please do for the show. @Leo
So my 2012 iMac got really sluggish this year. It had the fusion drive in it. I remembering you saying on your shows (when other people called in) that it would probably die soon. I even tried reinstalling the OS on it but still sluggish. I eventually hooked to an external SSD Via USB 3.0 and that brought it back to life. (I didn’t want to risk opening up the iMac and cracking the screen to put in an internal SSD). When I updated to Catalina, even with The external SSD, it would then freeze about a second every so often, so I bought a completely new iMac with 1 TB SSD. Even faster and better.
So are you saying I can expect my new iMac’s SSD to last the same time as my previous internal spinning fusion drive which was 7 years? I was thinking an SSD would last even longer? I’m just curious roughly how long I can expect this to last.
Tony
Chandler, AZ
Aka The Principal (I did a few video questions for iOS Today with a tie on and you said you felt like you were called to the principal’s office!)
Keep up the great work!
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I have SSDs now that are older than this, pretty sure. But there is one thing about Apple of the past that you need to be wary of. SSDs behave different when they get full than when they are empty. When they are empty, any empty sector is on the list of available sectors to use, and to wear level with. Once the disk gets full, there are less free sectors to wear level with. Not all older Apple devices properly supported TRIM. TRIM lets the OS tell the device “I don’t care about this sector any more.” So over time, any disk with any use would use all available sectors without TRIMing them, making it impossible for the disk to have free sectors available on demand. This slows down writes, frequently quite noticeably. Another thing about SSDs in general is that you can’t write just a single byte anywhere. No matter how small the write, a significant portion of the disk is affected. How much depends on the design of the drive, but you can probably expect the drive will need to rewrite as much as 8 to 32 sectors just to do a single byte update. For this reason, the drive will cache writes until it has enough data to make it worthwhile. And again, if the disk is mostly full, this makes that process even more difficult, as it works hard to shuffle items around to make enough room for the minimum page to write.
TL; DR : Keep lots of room on your SSD, and use it with an OS that supports TRIM and it shouldn’t slow down as much over time.
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The one thing not mentioned is the deterioration of the data over time if the SSD is not powered on. With a traditional HDD, the data is written and will remain for a very long period, as it is magnetically written to the disk.
An SSD uses charged memory cells, as the charge weakens and fails, data will be lost. Leaving an SSD in a cupboard for a long time can mean that chunks of the data are gone, when it is turned back on. But we are talking many months or a couple of years of “down time”. So they aren’t good for backups, for example.
In regular use by a home user, they should last for years. I have an old Sony laptop, which I upgraded to SSD about 4 years ago and the SSD is still going strong.
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I found an application called Drive X which I think helps me answer my question partially. It gives a good health report of my SSD. However, it would be great to know, if at all possible, under my average use, how long can I expect my SSD to last on average? Maybe an impossible thing to find out. I am just curious and, heck, if it does completely fail, then I can always buy an external and plug it into the Thunderbird 3 port with I am guessing similar speeds to the internal.
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And here’s a report of an external SSD that I use to clone my internal. Interesting that it is showing as failing. I only had the drive for about 6 months.
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Wow. That is an interesting program
The cynic in me says to check how long the manufacturer’s guarantee on the drive lasts. It’s usually carefully calibrated to the average life of the drive in normal use. Once you’re outside the guarantee period, the likelihood of failure will probably be a lot higher. It was always a good guide for spinning disks - cheapies might only get a year or so, mid-price were 3 years and the best drives were 5 years. You might get years beyond that, but you were best advised to back up frequently in case.
The thing is is that it’s internal and came with the iMac.
Oh yes of course! (slaps forehead) 
No way of finding out about that hardware…
That’s DriveDx - $19 - looks pretty cool. I don’t know how much I would trust it, however. SMART was hobbled by the drive manufacturers who didn’t want users getting scary warnings. (Google reported that 36% of their drive failures happened without any SMART warnings at all. https://en.wikipedia.org/wiki/S.M.A.R.T.) And it’s not clear how useful SMART is on non-SATA drives (like NVME).
Here’s the report on my fairly new MacBook Pro:
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