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One of my biggest questions is the lifetime of these drives. I know that flash memory has a certain number of write-cycles but has there been any study done on

by Nrsolis 15y ago

One of my biggest questions is the lifetime of these drives. I know that flash memory has a certain number of write-cycles but has there been any study done on how long these drives last in an almost constant write environment like OLTP?

pmh 15y ago
IIRC, SLC NAND has ~100,000 write cycles and MLC ~10,000 (enterprise-level SSDs almost exclusively use the former). I'm not aware of any recent studies specifically on durability, but given that there are no moving parts I'd imagine that SSDs last at least as long as mechanical drives. There's also this bit from the press release: "[The] 700GB drive [is] able to write 28 terabytes of data every day for five years."
- wtallis 15y ago
  There's a big tradeoff between reliability and density: 50nm MLC is good for around 10k cycles, but 34nm and 25nm MLC are rated in the 3k-5k range, and it's not clear yet whether 20nm MLC will be able to stay in that range. SLC is much more reliable, but also much less dense than MLC. It's easy to maintain overall device reliability (and performance) by having more spare area, but that negates a lot of the benefit of moving to a smaller process. (And the performance penalty from having fewer flash chips to stripe across for a given drive size also detracts from the smaller process size.)
rektide 15y ago
Warranty is key here. That and having prepared ops. Which is no different than it was with HD's. But for the sake of it, let's run the numbers. A 700GB drive being written at 2GB/s would fully cycle in 350 seconds. That's 86400/350 is 247 cycles a day (amusing 247 ~ 24/7 coincidence spotted). Assuming a 10,000 cycle life, that's 40 days of operation. Go to 100,000 cycle life and that a 400 day lifetime of non-stop full-speed writing. And worth every sweet cent of that somewhat short life, in this commenters opinion. I'm sure that the half rack of HD's it'd take to get this kind of IOPs wouldn't have an in any way improved expected lifetime cost. If you just need throughput the story may be a little different.
modeless 15y ago
"The P320h drive also provides enterprise-class levels of endurance with the 700GB drive able to write 28 terabytes of data every day for five years." Not only that, but the write endurance failure mode is benign: the drive simply becomes read only.

by Nrsolis 15y ago

pmh 15y ago

IIRC, SLC NAND has ~100,000 write cycles and MLC ~10,000 (enterprise-level SSDs almost exclusively use the former). I'm not aware of any recent studies specifically on durability, but given that there are no moving parts I'd imagine that SSDs last at least as long as mechanical drives. There's also this bit from the press release: "[The] 700GB drive [is] able to write 28 terabytes of data every day for five years."

wtallis 15y ago
There's a big tradeoff between reliability and density: 50nm MLC is good for around 10k cycles, but 34nm and 25nm MLC are rated in the 3k-5k range, and it's not clear yet whether 20nm MLC will be able to stay in that range. SLC is much more reliable, but also much less dense than MLC. It's easy to maintain overall device reliability (and performance) by having more spare area, but that negates a lot of the benefit of moving to a smaller process. (And the performance penalty from having fewer flash chips to stripe across for a given drive size also detracts from the smaller process size.)

rektide 15y ago

Warranty is key here. That and having prepared ops. Which is no different than it was with HD's. But for the sake of it, let's run the numbers. A 700GB drive being written at 2GB/s would fully cycle in 350 seconds. That's 86400/350 is 247 cycles a day (amusing 247 ~ 24/7 coincidence spotted). Assuming a 10,000 cycle life, that's 40 days of operation. Go to 100,000 cycle life and that a 400 day lifetime of non-stop full-speed writing. And worth every sweet cent of that somewhat short life, in this commenters opinion. I'm sure that the half rack of HD's it'd take to get this kind of IOPs wouldn't have an in any way improved expected lifetime cost. If you just need throughput the story may be a little different.

modeless 15y ago

"The P320h drive also provides enterprise-class levels of endurance with the 700GB drive able to write 28 terabytes of data every day for five years." Not only that, but the write endurance failure mode is benign: the drive simply becomes read only.