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Prevent SSD wear by using SmartSleep
Authored by: unforeseen:X11 on Jan 05, '11 11:15:22AM
Those concerned about SSD wear should read this report:
http://www.bitmicro.com/press_resources_debunking.php

Two calculations are in there:
  • The older assumes 100k cycles per cell, writing 3.4 Terabyte of data to a 160 GB SSD daily will leave your SSD functional for almost 13 years.
  • The newer assumes 2 million cycles per cell, constant (sic!) writing at 80 GB/sec on a 64 GB SSD will leave it intact for more than 50 years.
Details in the report. As SSDs shut down worn out cells data loss will almost never happen as you'll replace an ageing "disk" anyway.
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Performance also affected by unnecessary writes (no TRIM in Mac OSX)
Authored by: QuickSander on Jan 06, '11 02:20:16AM

Interesting article!

Still, it keeps puzzling me why there are a lot of users experiencing measurable slow down (on Mac OSX without TRIM support). Is this caused by the wear leveling algorithm for which it gets tougher and tougher to find unused cells??

If true, then reducing writes will still be beneficial to maintain write performance as long as Mac OSX does not support TRIM. So there are still other concerns than only the lifetime of an SSD to consider.

Edited on Jan 06, '11 02:32:50AM by QuickSander



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Performance also affected by unnecessary writes (no TRIM in Mac OSX)
Authored by: Makosuke on Jan 07, '11 04:50:31PM

"Still, it keeps puzzling me why there are a lot of users experiencing measurable slow down (on Mac OSX without TRIM support). Is this caused by the wear leveling algorithm for which it gets tougher and tougher to find unused cells??"

Sort of--the key word here is "without TRIM support"--to my knowledge all the reports of modern drives experiencing slowdowns over time have nothing to do with wear leveling or failed cells, but with the lack of TRIM support meaning that the drive is having to re-write large blocks of data even for small amounts of data transfer. The reason that this problem exists (and the reason for TRIM support) area heavily documented if you read around.

So while slowdown is most certainly an issue, and it's even possible that web cache would exacerbate it, the lack of TRIM has more to do with it than any kind of wear issues. And it's important to note that just because cells in the SSD wearing out aren't likely to be a problem, that doesn't mean the drive isn't going to fail--just that it's not likely to be failed data cells that cause the drive to die. It might only last a year, or it might last ten, but it's going to be controller of full-chip failure that kills it, not data wear.

Note, also, that SandForce drives have better firmware to deal with the data slowdown issues than older (or, to my knowledge, Intel) drives. In particular OWC's drives have firmware that deals VERY well with the MacOS's lack of TRIM support--every real-world test I've seen of their drives show consistent read/write performance no matter how hard the drive is stressed.



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A Sensible Approach to the Issue
Authored by: chucky23 on Jan 06, '11 07:52:16AM

"Those concerned about SSD wear should read this report: Press Resources Debunking"

Can we agree that there are many CONFLICTING reports being issued? There are also reports showing some bad real world outcomes with heavy wear on SSD's, and well as reports claiming it is a non-issue.

My take on the issue:

- I don't think the science is settled yet on this issue.

- I think this is a new technology where long-term issues will be discovered in the real world long-term.

- I think different manufacturers are experimenting with different solutions to the issue.

- I think folks involved in SSD manufacture and sales have an interest in pushing reports that take one particular side of the issue.

- In short, I don't think we yet know with anything even getting close to certainty about the long-term effects of heavy wear on SSD's.

So, I tend to take a balanced approach. I disable "hibernate & sleep" on my SSD laptops, since it's an ever-present source of VERY heavy writes. I try to leave my SSD's 50% empty to not put stresses on provisioning schemes.

Disabling "hibernate & sleep" doesn't bother me, since I can manage low battery situations on my own, without any real hassle.

Leaving my SSD's 50% empty doesn't bother me, since I don't need much local storage, because I keep my media on the LAN, and I can tunnel into my LAN when I'm traveling.

Those two steps seem like the low-hanging fruit to me.

Beyond those two simple steps, I don't worry. I don't put my Safari cache on a RAM disk. I don't change my behavior to avoid disk writes. I just enjoy the speed of my SSD.

Everyone is going to take different strategies, depending on their own needs. (If you're rich, don't worry, since you can just replace the SSD in 18 months. If you want to keep a machine with that SSD in it for 5 years, take some simple precautions, since the real verdict on the technology is in dispute.)



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A Sensible Approach to the Issue
Authored by: unforeseen:X11 on Jan 06, '11 08:38:12AM

If there was a "Like" button here, and I actually had a facebook account, I would hit it. ;)

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