SSD Write Endurance 25nm Vs 34nm

[Christopher]

Manufacturer's P/E rating assumes no recovery period between writes. If you allow for a recovery period, though, the write durability can be increased by quite a bit. Here's a paper on it, I think this was posted much earlier in the thread, but even if it was it's worth reposting.

http://www.usenix.org/event/hotstora...pers/Mohan.pdf

With a recovery period of about 100 seconds they observed a 10-fold increase in write endurance for 2-bit 50nm MLC. With a recovery period of 3-4 hours, you're looking at a 100-fold increase in write endurance (so MLC NAND that's rated for 10k P/E cycles would be able to handle closer to 1 million).

This is something to keep in mind when looking at how long these drives being tested last. All the drives here are being written to very aggressively, so there will be less of a recovery period. In theory, under a more modest desktop workload where the drives aren't being written to as rapidly, you could expect even greater write endurance than the results in this thread suggest.

For example, during testing the NAND in the 64GB Samsung 470 was being overwritten once every 115 seconds or so. That isn't a very long recovery period, based on the durability increase for 50nm MLC in the study, you could expect roughly a 9.3x increase in endurance over the manufacturer's rating. The 34nm NAND is rated for 5k, which means it should be able to handle about 46.5k P/E cycles in practice. This seems to agree reasonably well with where the drive actually died (about 39k P/E cycles). Smaller geometry NAND probably benefits less from the same recovery period, which could be why endurance ended up being lower.

Also I think I've mentioned this before, but just wanted to say thanks again to all those sacrificing their time and money to make this possible. This thread is a wealth of knowledge, lots of great information here on real world write endurance and SSDs in general.

If that ends up being anywhere near true, a large capcity, or slow writing drive would die of boredom before exhausting PE cycles. It probably takes the X25-V much, much longer to do what the Samsung did every ~115 seconds (not sure if that takes WA into the equation). If the recovery period really exists, the X25-V will be around for a while... or in the 470s case, it could just be that Samsung flash is really, really good. I guess you could make the case that the recovery period for the 470 overcame substantially higher write amplification, and had it been on par with the others at ~1.1WA it would still be chugging along.

..that reminds me...

Most of the available controllers on the market are already being tested -- except for the new SF, which I believe Anvil has covered. So there's the Toshiba, Samsung, Indilinx, Micron, SF1200, (possibly the SF2281), and the Intels. The only controllers I can think of that aren't being tested are the Phison and JMicron. The JMicron is terrible, and the Phison is only used in the Patriot Torqx 2 (with 32nm NAND). I can't really think of any other unique controller/flash combos that would help to diversify the test. I've bought several older drives in the past week as they've been on sale, but the drives are either already in the test (like the X25-V and Vertex Turbo) or pretty similar (an Agility60 w/ 34nm Intel) or not really appropriate (like an X25 E). I'd be willing to put up the new Agility60 for destruction, but I think that the Patriot Torqx might be more interesting. If anyone has any ideas for a good 32GB -64GB to test, I'll order one to throw on the fire.