RealBlackStuff wrote:All 840: NO.
850 Pro: YES
850 Evo: NO
I was wondering whether someone would post something like this. It's a harsh assessment, but one I basically agree with. I simply wouldn't take any chances with my data. Apologies if this has been discussed before, but I feel like writing today. I'm doing this from memory and it will hardly be the last word in accuracy. These are merely my opinions from reading Anandtech over the years.
First off, in terms of personal experience, I can only praise SSDs. Mine have all been reliable thus far. They include various, older, Samsung, Intel and Crucial drives in 3 different machines. I had one very early OCZ drive, which I quickly sold due to stuttering performance.
OCZ, as a company, have a bumpy history. I believe they used to release a lot of badly validated unreliable product. Eventually they went bankrupt and were bought by Toshiba, who retained the brand name. I really don't know why, because that name is mud with a lot of people. It's hard to say what their product is like today. I would stay away from it.
There are basically only 3 companies I would buy from in the consumer space, Samsung, Crucial and Intel. It's not like they haven't had problems too, but they are the big ones who have the most in-house expertise and the most control over their product. Samsung make everything themselves, flash memory, controllers and firmware. Crucial are the consumer arm of Micron who also produce flash memory and, while they use 3rd party controllers, I believe they are writing their own firmware. They also made a big deal about the amount of validation they do when they entered the market.
It's a similar story with Intel. They mostly produce everything themselves, except for some of their product lines they sourced 3rd party (Sandforce) controllers. While OCZ were merrily selling drives with those controllers, Intel spent a full year validating them and ironing out bugs. It's just a different mindset with the big companies, those who sell into the enterprise market as well.
One issue that a lot of consumer drives have is that they don't cope well with power failures. Not likely to happen with a laptop, you say? I'm not so sure. Looking at my hard disk light during shutdown, Windows 7 always seems to access it right before the machine turns itself off. The drive in my laptop (Samsung 830) reports quite a number of unexpected power-offs (via SMART) that I can't explain. My impression is that Windows and SSD power-offs aren't properly integrated and this leads to the SSD having to recover from time to time. Either that or it's a specific issue with my Thinkpad T520. Anyhow, SSDs do generally recover, but someone made a test (the link escapes me now) with several older drives, where they forced the issue. After 6,000 unexpected power losses only the Intel drives kept working flawlessly. That's validation for you. I believe many Crucial drives also have extra circuitry to handle power losses. Not sure about Samsung.
Coming to specific product lines, there is a general problem with flash memory quality going down. Every manufacturer adopts smaller and smaller process technologies year after year. This allows higher capacities and lower prices. And so, in today's flash memory cells, at around 20nm lithography or less, there are fewer electrons trapped than in flash memory cells from a few years ago that were produced with 34nm or 50nm lithography. This makes the memory harder to manage. In addition Samsung's budget lines store 3 bits in each cell ("TLC NAND"), whereas most everyone else stores 2 bits ("MLC NAND") these days.
TLC NAND is Samsung's way of being competitive, but it has led to problems with long-term data retention. After several months a significant number of users observed severe performance degradation reading old data that hasn't changed. No data loss, mind you, but this is why RealBlackStuff is advising you to stay away from the 840 and 850 Evo series. Not all of the 840 series are TLC, I think only the 840 Evo is, but basically he is telling you to go for what should be the best Samsung drive, the 850 Pro. That drive uses V(ertical)NAND, where Samsung have found a way to add more memory by stacking cells vertically. And it's very telling that, now they have the extra vertical space available, Samsung reverted back to a larger 40nm lithography.
So where does that leave us? Samsung have fixed the firmware for their 840 / Evo drives and this seems to have improved the situation for most users. Still, in my mind, TLC drives are tainted. Samsung were pushing a bit too hard with those designs for my taste. They were the earliest to fail in the torture test. To keep that in perspective, I have my 830 drive for over 2 years now and only about 10TB written to it during daily use. At this rate I have decades to go before getting into torture test territory. An 840 Evo, or any SSD, is just fine for most users. You'll never come near the failure points from the torture test. However I do think it's telling the 840 Evo was the first drive to show errors in the test and it also showed the above-mentioned other problems in real life. That's why I'd avoid it.
My recommendation, on a budget, would be for a Crucial M500 or M550. Older technology. Slightly larger lithography than their newer drives. Mature firmware and, speed-wise, much the same, I believe. For a higher performance option (on SATA3), I'd probably select the Samsung 850 Pro. Intel doesn't cater much for the consumer market at the moment and tends to be more expensive.