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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MrCommunistGen - Thursday, July 25, 2013 - link
YES! I've been excitedly waiting for this review since the announcement!Byte - Thursday, July 25, 2013 - link
Writes for the 120GB are still quite slow.chizow - Thursday, July 25, 2013 - link
That's nearly universal though for all the entry-level capacity SSDs on the market, it's similar to RAID 0, when you can write to symmetrical NAND packages you see a significant increase in write speeds.OUT FOX EM - Monday, July 29, 2013 - link
Speaking of RAID 0, if you'll notice, all the drives of 250GB and higher perform around the same. You are MUCH better off getting 4x250GB drives instead of the 1TB. With most models the cost will actually be about the same, but the speed of the RAID will be 4x faster as well while maintaining the same capacity.Of course there are other drawbacks like space inside your PC and amount of available SATA ports on your motherboard, for instance, but if those aren't a factor, buying multiple SSD's is a much better option in terms of performance. I don't see many reviews mention this fact.
Jorgisven - Thursday, August 1, 2013 - link
Much better in terms of performance, but I wouldn't recommend RAID 0 for 4 SSD hard drives. RAID6 is likely a better option, as it is fault tolerant without losing too much space. It's a bit of a personal decision, but the RAID concepts stand true whether it's SSD or not. Additionally, 4x250 is likely a good percentage more expensive than the already expensive 1TB SSD.Democrab - Thursday, August 15, 2013 - link
I'm not sure about you, but I'm only storing replaceable data on my SSDs...There are game saves but they're automatically put on Google Drive too so I get backups easily, it's easy to set something like that up and then just get the benefits of RAID0 although I'd be using a RAID card as the chipset would likely bottleneck it.yut345 - Thursday, December 12, 2013 - link
I agree. Due to the volatile nature of SSDs, and the fact that if they go down your data can't really be recovered like it could be on mechanical drive, I do not plan to store anything on the drive that I don't also back up somewhere else.m00dawg - Friday, August 23, 2013 - link
With only 4 drives, a RAID10 would be much preferable. 1/2 the available space (same as a 4 drive RAID6 in this case), but without the need to calculate parity, worry (as much) about partitioning alignment, and you can still handle up to 2 drive failures (though only if they are on different stripes).fallaha56 - Friday, September 19, 2014 - link
sorry but disagree this will defeat the point unless you're on a top-end raid controller -and then you get no TRIMwhen there's no moving parts reliability becomes much less of an issue, esp for an OS drive with cloud and local backup like most of us high-end users do
Stas - Tuesday, September 24, 2013 - link
That's what I did for the recent laser data processing builds. 4x250GB 840s and a 1TB HDD for nightly backup. Only data is stored on the array. Speeds are up to 1600MB/sec. Needless to say, the client is very happy :)