Samsung SSD 840 EVO 250GB & 1TB TLC NAND Drives Tested

MojoKid writes "Samsung has been aggressively bolstering its solid state drive line-up for the last couple of years. While some of Samsung's earlier drives may not have particularly stood-out versus the competition at the time, the company's more recent 830 series and 840 series of solid state drives have been solid, both in terms of value and overall performance. Samsung's latest consumer-class solid state drives is the just-announced 840 EVO series of products. As the name suggests, the SSD 840 EVO series of drives is an evolution of the Samsung 840 series. These drives use the latest TLC NAND Flash to come out of Samsung's fab, along with an updated controller, and also feature some interesting software called RAPID (Real-time Accelerated Processing of IO Data) that can significantly impact performance. Samsung's new SSD 840 EVO series SSDs performed well throughout a battery of benchmarks, whether using synthetic benchmarks, trace-based tests, or highly-compressible or incompressible data. At around $.76 to $.65 per GB, they're competitively priced, relatively speaking, as well."

Comments

Call me old fashion

[Taco Cowboy]

How many effective READ/WRITE cycle can the chip in SSD perform, before they start degrading ?

Has there been any comparison made in between the reliability (eg read/write cycles) of old fashion spinning-plate HD versus that of SSD ?

Re:Call me old fashion

[beelsebob]

Yes, many sites have done the maths on such things. The conclusion "finite life" is not the same thing as "short life". SSDs will in general, outlast HDDs, and will in general die of controller failure (something which affects HDDs too), not flash lifespan.

The numbers for the 840 (which uses the same flash, with the same life span) showed that for the 120GB drive, writing 10GB per day, you would take nearly 12 years to cause the flash to fail. For the 240/480/960 options for the new version you're looking at roughly 23, 47 and 94 years respectively. Given that the average HDD dies after only 4 years (yes yes yes, we all know you have a 20 year old disk that still works, that's a nice anecdote), that's rather bloody good.

Re:Call me old fashion

[beelsebob]

Yes, they were solved in a firmware patch a long time ago.

Re:Call me old fashion

[beelsebob]

The problem with such tests of writing as much as you can as fast as you can is that they're rather deceptive. They don't allow TRIM and wear levelling to do their thing (as they normally would), and hence show a much worse scenario than you would normally be dealing with. Actual projections of real life usage patterns writing ~10GB to these drives per day show you can get their life span in years (specifically the 840 we're talking about here) by dividing the capacity (in gigabytes) by 10.

Re:Call me old fashion

[Gaygirlie]

How many effective READ/WRITE cycle can the chip in SSD perform, before they start degrading ?

They don't start degrading, per se. Performance-degradation is all due to wear-levelling and the amount of free blocks on the drive, and that varies between manufacturers. Generally the advice is to have atleast 20% of the drive free at all times for wear-levelling and TRIM to work efficiently and in such a situation there should be no performance-degradation.

As for reading and writing cells? Well, you can read a cell indefinitely. You cannot write to cells forever, however, and once the limit comes there is 100% degradation -- so to speak -- as in that that cell cannot be written to ever again. It just goes from 100% to 0%, so using the term "degradation" for that still seems useless. I'll repeat, though, that it can still be read from even if it can't be written to.

Has there been any comparison made in between the reliability (eg read/write cycles) of old fashion spinning-plate HD versus that of SSD ?

Plenty, but how much those comparisons actually cover and how reliable they are is subject to debate. Generally the consensus is that SSDs are more reliable nowadays as full-on controller-failures are very rare and since the SSDs can still be read from even if they hit the maximum amount of writes that means your data is quite a lot safer in the long run -- if a regular, mechanical drive can't write to some sector it most likely can't read it either, and that means your data is as good as gone.

Re:Call me old fashion

[AmiMoJo]

It depends on what you use it for. I managed to wear out an Intel XM-25 160GB SSD a few years ago by hitting the 14TB re-write limit.

Modern SSDs so a lot of compression and de-duplication to reduce the amount of data they write. If your data doesn't compress or de-duplicate well (e.g. video, images) the drive will wear out a lot faster. I think what did it for me was building large databases of map tiles stored in PNG format. Intel provide a handy utility that tells you how much data has been written to your drive and mine reached the limit in about 18 months so had to be replaced under warranty.

Re:Call me old fashion

[Rockoon]

Intel provide a handy utility that tells you how much data has been written to your drive and mine reached the limit in about 18 months so had to be replaced under warranty.

You were (amplified?) writing 32.8 GB per day, on average.

Clearly you will run into SSD erase-limit problems at such a rate, but such workloads normally turn out to not be tasks that actually benefit from an SSD to begin with (32.8GB/day = 380KB/sec, so the devices speed wasnt actually an issue for you)

You were either very clever and knew you would hit the limit and get a free replacement, or very foolish and squandered the lifetime of an expensive device when a cheap deice would have worked.

In any event, in general the larger the SSD the longer its erase-cycle lifetime will be. For a particular flash process its a completely linear 1:1 relationship, where twice the size buys twice as many block erases (a 320GB SSD on the same process would have lasted twice as long as your 160GB SSD with that work load)

Re:Call me old fashion

[Anonymous Coward]

Power failure?

You don't have a UPS or other standby power source available? You know its 2013 right...

Willing to spend hundreds on an ultra fast STORAGE device and have no backup power available? really? come on...

That's some messed up priorities there... Spend a hundred bucks on a UPS already.

Then you don't ever have to worry about data corruption. Or the much more common... Loss of unsaved work due to power failure...

Re:Call me old fashion

[Rockoon]

Indeed. I just don't see how the erase-limit issue applies for most people. The most common activity where it might apply is in a machine used as a DVR (dont use an SSD in a DVR), with the next being a heavily updated database server (you may still prefer the SSD if transaction latency is important.)

For people that use their computers for regular stuff like browsing the web, streaming video off the web, playing video games, and software development.. then get the damn SSD -- its a no-brainer for you folks.. you will love it and it will certainly die of something other than the erase-limit long before you approach that limit.

Re:Call me old fashion

[Rockoon]

Technically it becomes less and less reliable each time they do a die shrink on the flash. Adding a whole extra bit level makes things worse still. In the early 2000s you were looking at 100'000 P/E cycles, maybe a million for the really good stuff. Good TLC memory seems to be rated around 3000, with a figure of 1000 being widely quoted, and in some cases, less.

Lets not neglect the fact that while every die shrink does reduce the erase-limit per cell, it also (approximately) linearly increases the number of cells for a given chip area. In other words, for a given die area the erase limit (as measured in bytes, blocks, or cells) doesnt actually change with improving density. What does change is overall storage capacities and price.

When MLC SSD's dropped from ~2000 cycles per cell to ~1000 cycles per cell, their capacities doubled (so erases per device remains about constant) and prices also dropped from ~$3/GB to about ~$1/GB. Now MLC SSD's are around ~600 cycles per cell, their capacities are larger still (again erases per device remain about constant), and they are selling for ~$0.75/GB (and falling.)

By every meaningful measure these die shrinks improve the technology.

So now lets take it to the (extreme) logical conclusion, where MLC cells have exactly 1 erase cycle (we have a name for this kind of device.. WORM: Write Once Read Many.) To compensate, the device capacities would be about 600 times that of todays current capacities, so in the same size package as todays 256 GB SSD's we would be able to fit a 153 TB SSD WORM drive, and it would cost about $200.

Re:Call me old fashion

[hackertourist]

(32.8GB/day = 380KB/sec, so the devices speed wasnt actually an issue for you)

That's an odd way to look at it. You assume that GP spreads out his writes evenly over 24h, and has no desire to speed things up.

Re:Call me old fashion

[AmiMoJo]

In my case having an SSD made a huge impact. I was using offline maps of a wide area build from PNG tiles in an sqlite database with RMaps on Android. Compiling the databases was much faster with an SSD. I was doing it interactively, so performance mattered.

I can only tell you what I experienced. I installed the drive and I didn't think about it wearing out, just carried on as normal. The Intel tool said that it had written 14TB of data and sure enough writes were failing to the point where it corrupted the OS and I had to re-install.

I was using Windows 7 x64, done as a fresh install on the drive when I built that PC. I made sure defragmentation was disabled.

I'm now wondering if the Intel tool doesn't count bytes written but instead is some kind of estimate based on the amount of available write capacity left on the drive. I wasn't monitoring it constantly either so perhaps it just jumped up to 14TB when it noticed that writes were failing and free space had dropped to zero.

It was a non-scientific test, YMMV etc etc.

Re:Not paying for TLC at that price

[beelsebob]

Except if you actually bothered to educate yourself, you'd find that at the capacities samsung is offering you, if you write to them at 10GB a day, every day, they'll last entirely respectable times (12,23,47,94 years respectively for 120,240,480 and 960GB drives).

Hot vs Crazy

[bdwoolman]

Here's the thing. SSDs are now more reliable than when this guy logged this report.

But are still maybe not as steady Eddie as a good-quality HDD. But we still want them because having an SSD boot drive changes the whole computing experience due to their awesome speed. And since we are good about backups (Are we not?) we can be relaxed as we ride the SSD smokin' fast Roller Coaster. SSD or HDD then what's the problem if we have data security. Both are gonna FAIL. So what if Miss SSD stabs me for no good reason? It was a helluva ride, Bro. And well worth the stitches. I do wish SLC NAND was not priced out of reach, but, hey, when it comes to hottness we take what we can get. Right?

Okay. This is Slashdot we get no hottiness...no hottiness at all.. No no no hottiness. It's pathetic really. ....