SSD wear leveling count at 90% after 7 months

vladobizik

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Original poster
Aug 21, 2012
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Slovakia
I have had a 2013 MBA since last October (i.e. about 7 months), it has a 512GB Samsung SSD and I use it daily and quite heavily (it's my primary and only computer). I used DriveDX to check the SSD's health and it reports that its "wear leveling count" is at 90% (see attachment). Is it a normal value? Does it mean I am 10% into the drive's lifecycle, or something worse or better?
Thank you very much.
 

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flowrider

macrumors 603
Nov 23, 2012
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^^^^Looks to me like the utility is telling you that you still have 90% of your battery's capacity left.

Lou
 

vladobizik

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Original poster
Aug 21, 2012
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^^^^Looks to me like the utility is telling you that you still have 90% of your battery's capacity left.

Lou
Nope, it's a disk/SSD diagnostic utility. Plus, I am positively sure at the time of taking the screenshot the battery was at 30% or so :)
 

Weaselboy

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Jan 23, 2005
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I have had a 2013 MBA since last October (i.e. about 7 months), it has a 512GB Samsung SSD and I use it daily and quite heavily (it's my primary and only computer). I used DriveDX to check the SSD's health and it reports that its "wear leveling count" is at 90% (see attachment). Is it a normal value? Does it mean I am 10% into the drive's lifecycle, or something worse or better?
Thank you very much.
I have the same 2013 MBA with a 128GB flash drive and the same app, and yes, that is exactly what it means. Each NAND cell has a finite number of program/erase cycles and this is an indication of how many you have used up.

Here is mine.

 

jsd79

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Nov 29, 2013
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I have the same 2013 MBA with a 128GB flash drive and the same app, and yes, that is exactly what it means. Each NAND cell has a finite number of program/erase cycles and this is an indication of how many you have used up.
By this logic, which I can't dispute because I don't have the necessary technical knowledge, it would seem the MBA's SSD can be expected to last just about three years before it is spent. My guess is that for most users it would probably last longer, though. But that's just my guess. On the bright side, I've had old-fashioned hard drives with shorter lifespans!
 

Weaselboy

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By this logic, which I can't dispute because I don't have the necessary technical knowledge, it would seem the MBA's SSD can be expected to last just about three years before it is spent. My guess is that for most users it would probably last longer, though. But that's just my guess. On the bright side, I've had old-fashioned hard drives with shorter lifespans!
I think your maths are off :). If you go by my stats, my MBA's flash storage would last around ten years at my current usage pattern.
 

RightMACatU

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Jul 12, 2012
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I have the same 2013 MBA with a 128GB flash drive and the same app, and yes, that is exactly what it means. Each NAND cell has a finite number of program/erase cycles and this is an indication of how many you have used up.

Here is mine.

Image
Would this mean that you now have about 115GB useful left? (90% of 128GB)
 

Weaselboy

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Would this mean that you now have about 115GB useful left? (90% of 128GB)
I don't think there is a linear relationship like that because most flash drives set aside some space for this wear leveling. So one would not see a loss of usable space until that space has been used up.

Also, this is an indicator of wear across all the NAND cells. So for example, even if this number was 50%, it would mean all the available NAND cells had used half their lifetime, but would still be working and the drive would still show full capacity.
 
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SDColorado

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Nov 6, 2011
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Wear leveling attempts to ensure that one part of the flash drive does not prematurely fail by ensuring that erasures and re-writes are distributed evenly across the medium.

So the 90% wear level should indicate that the entire 128GB Drive has used 10% of its expected life and has 90% remaining. No indication of a loss of any of that 128GB. You should not expect to lose any capacity of the drive until the drive reaches an age where it would begin to possibly fail, down in the low single digits I would think.

By DriveDX's own description, a drive will often hit 95% quickly during its first week of drive lifetime and then the rate will slow after that.
 

copa

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Nov 8, 2013
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is there a free way to look this up? Got myBMA in December and I'm just curious to see how it holds up.
 

Mrbobb

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Aug 27, 2012
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U know what, I don't want to know. Unless I can do something about it, it's just stressing for nothing.
 

Weaselboy

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U know what, I don't want to know. Unless I can do something about it, it's just stressing for nothing.
I agree one does not want to obsess over things like the write count, but there are SMART attributes that can provide advance warning of impending drive failure and that would be good to know.
 

dalupus

macrumors regular
Jul 19, 2011
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U know what, I don't want to know. Unless I can do something about it, it's just stressing for nothing.
You can do "something" about it. When you drive is nearing the end of it's lifespan you can replace it.

Although, I doubt you would have your computer anymore when you did.

I have a mid 2011 mac and mine shows 80%

The chance of me still having this machine 12 years from now when this is approaching 0% is nil.
 

smithrh

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Feb 28, 2009
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I agree one does not want to obsess over things like the write count, but there are SMART attributes that can provide advance warning of impending drive failure and that would be good to know.
I don't disagree with what you said at all, but:

Sadly enough, I've yet to get a SMART warning before a failure. I'd place more stock in it had it actually warned me...
 

alphaod

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Feb 9, 2008
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NYC
So you have use 10% and have 90% left; unless you do have writes I don't see this being much of a problem.
 

gnasher729

macrumors P6
Nov 25, 2005
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I have had a 2013 MBA since last October (i.e. about 7 months), it has a 512GB Samsung SSD and I use it daily and quite heavily (it's my primary and only computer). I used DriveDX to check the SSD's health and it reports that its "wear leveling count" is at 90% (see attachment). Is it a normal value? Does it mean I am 10% into the drive's lifecycle, or something worse or better?
Thank you very much.
Only the people creating that utility might know, and even they probably don't :D

You have your Time Machine backup (you have a Time Machine backup, right? ), so if the SSD drive breaks within 12 months it will be fixed under warranty, and you have 12 months time to buy AppleCare which will cover it for three years, so it will be fixed for free for three years. And having a Time Machine backup, you just restore your backup, and everything is fine.

Would this mean that you now have about 115GB useful left? (90% of 128GB)
No.

On an SSD drive, every 128KB block can be written a certain number of times, say 100 times (I make up this number, I have no idea what the actual number is). Now you have blocks that are written a lot, and others are never written at all. Say you have a 100 MB music album, those 100 MB will be written once and never be written again as long as you keep the music.

When the SSD drive notices that some blocks are written a lot (say 90 times) it swaps them with blocks that are used very little. So your music album moves to a part of the drive that has already been written 90 times, but that's Ok because it is probably not going to be written again. And the data that was written again and again is now in a fresh area with only one or two writes so far.

So you have all the 128 GB available, until suddenly everything reaches the write limit and breaks down. Like your car, which doesn't slow down when the tank is half empty. When the tank is empty, it stops. Until then, it drives just fine.
 
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maflynn

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May 3, 2009
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Great utility, I downloaded it for my Mac Mini, and I'll grab it for my rMBP.

My Mac Mini's life is 100% which is nice, its a lightly used computer so that makes sense. My rMBP is more heavily leveraged with vmware running as well as Aperture
 

happyslayer

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Feb 3, 2008
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Glendale, AZ
Interesting. I just downloaded the demo and my 11" Air from June 2013 shows 97%. Nice. Though I do use my laptop quite a bit, it is mostly for Internet, some email and writing. My file sizes are very small, generally, so maybe that's why it's so high. Regardless, I'm not complaining.

On a side note, I don't understand why the company is charging $20.00 for an app that doesn't seem like it does all that much. Maybe it will run in the background or something, to warn you (I didn't read the full product description) but it really doesn't seem like I'd use it all that often--maybe every 6 months or so--so $20 seems a bit steep. JMO