SSD Write Limits? A Concern?

[michaelscott]

My 2006 MBP just bit the dust so I'm looking into a new iMac. I've been wanting a SSD for my workflow which includes using:

• Photoshop
• Coda
• Transmit
• Tower
• Chrome/Safari/Firefox
• Things
• Occasional iTunes listening
• Dropbox

It sounds like SSDs are, in theory, more reliable. I've heard a lot about write limits and had concerns. This will be a computer for my wife and I and we want to ensure it lasts us at least 4-5 (hopefully more) years. That being said, should we really be concerned with it? What does a real life scenario look like to go over the write limit on the Apple SSDs?

 

[Hellhammer]

Apple's SSDs use 34nm NANDs, which have 5000 P/E cycles. If the capacity is 128GB, then you can theoretically write up to 640 000GB, or 640TB of data into it before the NAND wears out. 5 years has 1 826 days (since there is at least one leap year) so that means you would have to write 351GB to the drive, everyday. That would be overwriting the whole drive 2.7 times, everyday.

Of course, this is the theoretical approach. In real world, some of the NANDs are filled with data that won't often be deleted (such as system files). Thus most of your writes are concentrated on a few NANDs. Even then, it's highly unlikely that you will be able to wear out your SSD before the NANDs lose their charge after about 10 years.

This article does good job explaining this.

 

[michaelscott]

Thank you, HellHammer, that helps out a great deal.

I know the value of an SSD changes by user and workflow, but would I see a great deal of benefit from an SSD? I do web design and frequently use Photoshop, Illustrator, Coda, Transmit, Tower (Git GUI app), and Chrome, Safari, and Firefox simultaneously.

Obviously launch times would increase, but would I see much benefit or would an SSD be more for a user constantly importing movies and images into high-end pro apps like FCP and Lightroom?

 

[michaelscott]

Apple's SSDs use 34nm NANDs, which have 5000 P/E cycles. If the capacity is 128GB, then you can theoretically write up to 640 000GB, or 640TB of data into it before the NAND wears out. 5 years has 1 826 days (since there is at least one leap year) so that means you would have to write 351GB to the drive, everyday. That would be overwriting the whole drive 2.7 times, everyday.

Of course, this is the theoretical approach. In real world, some of the NANDs are filled with data that won't often be deleted (such as system files). Thus most of your writes are concentrated on a few NANDs. Even then, it's highly unlikely that you will be able to wear out your SSD before the NANDs lose their charge after about 10 years.

This article does good job explaining this.

Are the Apple SSDs and controllers in the same league as the ones mentioned in that article, Hellhammer? How closely do they fit the "no worries" in the write limit department?

 

[Hellhammer]

Thank you, HellHammer, that helps out a great deal.

I know the value of an SSD changes by user and workflow, but would I see a great deal of benefit from an SSD? I do web design and frequently use Photoshop, Illustrator, Coda, Transmit, Tower (Git GUI app), and Chrome, Safari, and Firefox simultaneously.

Obviously launch times would increase, but would I see much benefit or would an SSD be more for a user constantly importing movies and images into high-end pro apps like FCP and Lightroom?

If you store the projects in the SSD, then you will definitely see an improvement in performance. Otherwise it's harder to say. Any tasks that involves disk I/O will be sped up but most tasks don't need it, at least not in extensive amounts.

Are the Apple SSDs and controllers in the same league as the ones mentioned in that article, Hellhammer? How closely do they fit the "no worries" in the write limit department?

Apple's SSDs seem to pretty good in this category. They aren't as good as SandForce ones because there is no real time compression but Apple's SSDs are quite average.

 

[TheEmpty]

Apple's SSDs use 34nm NANDs, which have 5000 P/E cycles. If the capacity is 128GB, then you can theoretically write up to 640 000GB, or 640TB of data into it before the NAND wears out. 5 years has 1 826 days (since there is at least one leap year) so that means you would have to write 351GB to the drive, everyday. That would be overwriting the whole drive 2.7 times, everyday.

Of course, this is the theoretical approach. In real world, some of the NANDs are filled with data that won't often be deleted (such as system files). Thus most of your writes are concentrated on a few NANDs. Even then, it's highly unlikely that you will be able to wear out your SSD before the NANDs lose their charge after about 10 years.

This article does good job explaining this.

Thanks Hellhammer, registered just to upvote that! Was thinking about buying the air (next rev), but talked myself out of it worrying that I might ruin the SSD since as a developer I have a lot of logs that write a ton, compiling, etc. but all that seems silly now. I assume that the frequency doesn't matter then?

 

[Hellhammer]

Thanks Hellhammer, registered just to upvote that! Was thinking about buying the air (next rev), but talked myself out of it worrying that I might ruin the SSD since as a developer I have a lot of logs that write a ton, compiling, etc. but all that seems silly now. I assume that the frequency doesn't matter then?

You mean CPU frequency? It might affect some tasks but in general, those CPU upgrades are fairly small, about 10%, so it might be better to just save the cash.

 

[TheEmpty]

You mean CPU frequency? It might affect some tasks but in general, those CPU upgrades are fairly small, about 10%, so it might be better to just save the cash.

That's not what I meant, but still that's good to know, I meant the frequency (of use) of writing to the SSD, does that matter? Like how it's bad to charge a battery halfway and take it off and use it, (I've been told it's best to charge at 20% 'till full, but I really don't know jack about computer electronics)

 

[BlackViper]

The only real downside to SSDs that I know of is Capacity; 3.5" HDDs are under $0.05/GB while SSDs are close to $2/GB. It's likely a more noticeable improvement over a processor upgrade and you can easily upgrade the RAM anytime in the future.

 

[Hellhammer]

That's not what I meant, but still that's good to know, I meant the frequency (of use) of writing to the SSD, does that matter? Like how it's bad to charge a battery halfway and take it off and use it, (I've been told it's best to charge at 20% 'till full, but I really don't know jack about computer electronics)

Shouldn't have any real difference. The more you use it, the more P/E cycles are consumed of course but it's very unlikely that even a heavy user could wear out the NANDs in less than several years. It's doesn't matter is it 20% full or 80% full, as long as you have some space for swap file and stuff (~5GB should be more than fine), everything should be okay.