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]

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

[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.