Samsung SSD 840 EVO Review: 120GB, 250GB, 500GB, 750GB & 1TB Models Tested
by Anand Lal Shimpi on July 25, 2013 1:53 PM EST- Posted in
- Storage
- SSDs
- Samsung
- TLC
- Samsung SSD 840
Endurance
Samsung isn't quoting any specific TB written values for how long it expects the EVO to last, although the drive comes with a 3 year warranty. Samsung doesn't explicitly expose total NAND writes in its SMART details but we do get a wear level indicator (SMART attribute 177). The wear level indicator starts at 100 and decreases linearly down to 1 from what I can tell. At 1 the drive will have exceeded all of its rated p/e cycles, but in reality the drive's total endurance can significantly exceed that value.
Kristian calculated around 1000 p/e cycles using the wear level indicator on his 840 sample last year or roughly 242TB of writes, but we've seen reports of much more than that (e.g. this XtremeSystems user who saw around 432TB of writes to a 120GB SSD 840 before it died). I used Kristian's method of mapping sequential writes to the wear level indicator to determine the rated number of p/e cycles on my 120GB EVO sample:
| Samsung SSD 840 EVO Endurance Estimation | |||||||
| Samsung SSD EVO 120GB | |||||||
| Total Sequential Writes | 4338.98 GiB | ||||||
| Wear Level Counter Decrease | -3 (raw value = 35) | ||||||
| Estimated Total Writes | 144632.81 GiB | ||||||
| Estimated Rated P/E Cycles | 1129 cycles | ||||||
Using the 1129 cycle estimate (which is an improvement compared to last year's 840 sample), I put together the table below to put any fears of endurance to rest. I even upped the total NAND writes per day to 50 GiB just to be a bit more aggressive than the typically quoted 10 - 30 GiB for consumer workloads:
| Samsung SSD 840 EVO TurboWrite Buffer Size vs. Capacity | |||||||
| 120GB | 250GB | 500GB | 750GB | 1TB | |||
| NAND Capacity | 128 GiB | 256 GiB | 512 GiB | 768 GiB | 1024 GiB | ||
| NAND Writes per Day | 50 GiB | 50 GiB | 50 GiB | 50 GiB | 50 GiB | ||
| Days per P/E Cycle | 2.56 | 5.12 | 10.24 | 15.36 | 20.48 | ||
| Estimated P/E Cycles | 1129 | 1129 | 1129 | 1129 | 1129 | ||
| Estimated Lifespan in Days | 2890 | 5780 | 11560 | 17341 | 23121 | ||
| Estimated Lifespan in Years | 7.91 | 15.83 | 31.67 | 47.51 | 63.34 | ||
| Estimated Lifespan @ 100 GiB of Writes per Day | 3.95 | 7.91 | 15.83 | 23.75 | 31.67 | ||
Endurance scales linearly with NAND capacity, and the worst case scenario at 50 GiB of writes per day is just under 8 years of constant write endurance. Keep in mind that this is assuming a write amplification of 1, if you're doing 50 GiB of 4KB random writes you'll blow through this a lot sooner. For a client system however you're probably looking at something much lower than 50 GiB per day of total writes to NAND, random IO included.
I also threw in a line of lifespan estimates at 100 GiB of writes per day. It's only in this configuration that we see the 120GB drive drop below 4 years of endurance, again based on a conservative p/e estimate. Even with 100 GiB of NAND writes per day, once you get beyond the 250GB EVO we're back into absolutely ridiculous endurance estimates.
Keep in mind that all of this is based on 1129 p/e cycles, which is likely less than half of what the practical p/e cycle limit on Samsung's 19nm TLC NAND. To go ahead and double those numbers and then you're probably looking at reality. Endurance isn't a concern for client systems using the 840 EVO.
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halbhh2 - Saturday, July 27, 2013 - link
Exactly. I found that even moving up from 8GB to 16GB had a great effect for me with an old Samsung F3 hard drive. The difference: after just 30 minutes from boot, loading an often used program like iTunes (for podcasts) was very similar to the speed on my laptop which has an 830 SSD and only 4GB. Both load in about 4 seconds, and the 16GB desktop loads so fast because it has had time to cache a lot of iTunes. Before the ram upgrade, that load time for iTunes on the desktop computer was about 14 seconds. Quite a difference due to windows 7 caching. The extra improvement I'd get from installing an SSD onto the desktop computer now would be modest, since I usually only need to reboot once or twice in a week. Still, the sweet spot of price/performance for me is approaching, probably around $60-$70, and that won't be long.Klimax - Sunday, July 28, 2013 - link
It's in wrong place. Unlike OS level caching (at least in Windows), which is in cooperation between memory manager, cache manager and file system driver, this is too low in the chain and sees only requests but nothing else and also takes memory from OS and takes too few.Coup27 - Thursday, July 25, 2013 - link
Typo: "although I wouldn't recommend deploying the EVO in a write heavy serve Microsoft's eDrive standard isn't supported at launch"Excellent article. Samsung continue to push SSDs and I'm really excited about RAPID. Is the 840 Pro due for a successor any time soon? I am selling my current ATX Sandy Bridge + 830 and getting a mITX Haswell + (840 Pro?) and want the fastest Samsung consumer SSD available and I'd be gutted to buy an 840 Pro to see it's successor released a few weeks later.
vLsL2VnDmWjoTByaVLxb - Thursday, July 25, 2013 - link
Another typo last page:"Even though its performnace wasn't class leading, it was honestly good enough to make the recommendation a no-brainer. "
JDG1980 - Thursday, July 25, 2013 - link
Will there be an 840 EVO Pro coming out later? To me, TLC is still a deal-breaker.By the way, what happens if power goes out during a TurboWrite (before the data has been written to the normal storage space)? Does this result in data loss, or, worse, bricking? I'd suspect Samsung at least avoided the latter, but I'd like to see some confirmation on this.
sherlockwing - Thursday, July 25, 2013 - link
I guess you didn't read the Endurance part of the review? Even if you write 100GiB a day all of those drives last longer than their warranty( 3 years), that's more than enough endurance.Coup27 - Thursday, July 25, 2013 - link
Some people just don't want to accept the facts. TLC could get to 99.9% of MLC endurance and people would still want MLC. I've been deploying 840's in a light duty enterprise environment and they've been fine. The only reason I use MLC at home is because I want the absolute fastest performance and I can afford it, not that I actually need it.Oxford Guy - Thursday, July 25, 2013 - link
The SanDisk Extreme 240 was just on sale for $150. TLC NAND still seems like a solution in need of a problem.Spunjji - Friday, July 26, 2013 - link
You can approach TLC pricing with an MLC drive in a sale, but the fact remains that when it comes to actual sustainable production pricing TLC NAND has a 50% density (and thus manufacturing cost advantage) over MLC. Given that NAND price determines drive cost and drive costs are the primary barrier of entry to SSDs, I'm fairly sure it has a problem to solve.FWIW I have not seen any drive touch the 120GB 840's price here in the UK, on sale or otherwise.
Oxford Guy - Friday, July 26, 2013 - link
However, there is also the problem of increasing latency and lifespan from node shrinkage.