
Micron Announces 5100 Series Enterprise SATA SSDs with 3D TLC NAND - DiabloD3
http://www.anandtech.com/show/10886/micron-announces-5100-series-enterprise-sata-ssds-with-3d-tlc-nand
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ChuckMcM
So where is the Cross Point technology[1] already?

[1] [https://newsroom.intel.com/news-releases/intel-and-micron-
pr...](https://newsroom.intel.com/news-releases/intel-and-micron-produce-
breakthrough-memory-technology/)

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russdill
Is it OK to call it PCM now?

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ChuckMcM
In terms of vaporware or in terms of technology? It's clearly not PCM as a
technology.

FWIW an anonymous source emailed me that early next year there would be more
news on this front. But I'll believe it when I see it.

~~~
russdill
I mention it because the core storage technology is quite clearly phase change
memory, it's the interconnect that is unique (especially the intergrated
ovonic threshold switch). But for the longest time, Intel/Micron have not
wanted to associated the technology with previous PCM technologies even going
so far as to deny it is PCM in the initial release press conferences.

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Dylan16807
I'm rather unsure why you would want to use TLC configured as 60% spare.
Wouldn't the same amount of flash at two bits per cell be much faster and
longer lasting?

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cjensen
When you program a flash cell, you first erase it, then you program it with a
new value. Each erasure wears the cell out, so the more bits-per-cell, the
longer the flash memory will last.

It may also be faster: to read a cell you have to address it and then measure
its value. With more bits per cell, you read/write more bits per address
cycle.

~~~
Dylan16807
These cells are nanometer-scale. Having fractional charges is _extremely_
subtle. It is significantly slower to read and write multiple bits, and it
takes a lot fewer writes until it doesn't have enough precision to support
that use.

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imaginenore
The price, considering the specs, doesn't make any sense.

I already can buy SSDs under 45 cents/GB, with more IOPS and faster sequential
writes.

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cjensen
These are Enterprise class drives.

In SSDs, the big difference between Enterprise and Consumer is endurance.
Flash memory wears out over time and the firmware manages the wear and maps
out bad sectors over time. Eventually, too much wears out and the drive can no
longer be written to, or is too slow to usably write to. The endurance spec
tells you how much data you can expect to write before the drive must be
replaced.

Micron sells both consumer and enterprise drives. The consumer 1100 SSDs max
out at 400TB endurance which is fantastic for a consumer drive. These
enterprise 5100 drives max out at 17.6PB endurance -- that's 44X better!

If you have an application which writes a lot of data, you should be
evaluating whether or not you need something like this.

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tamcap
Hasn't there been an article on HN recently that showed consumer grade drive
endurance testing? I believe many exceeded the endurance spec manyfold.

~~~
cjensen
There is some uncertainty in the numbers, so the manufacturers quote fairly
conservative numbers. In recent years flash cells have become a bit more
fragile and the process technology has changed multiple times, so good past
results on endurance testing are not necessarily indicative of future results.

I've personally burnt out a set of SSDs installed in a RAID-6. They lost no
data and failed no writes, but they had become unusably slow -- less than a
tenth of their original write speed.

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wtallis
What kind of SSDs were these, and how much writing had they been subjected to?
If the flash was really wearing out, I'd expect read performance to also
suffer significantly as LDPC soft decode error correction was required to
recover the data intact. If only write speed was degrading and if you weren't
thoroughly hammering the drives with writes around the clock, then you might
merely have filled up the drives with a RAID configuration that didn't pass
through TRIM commands.

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cjensen
If the read speed had degraded, I didn't notice since the RAID controller is
the bottleneck in this particular system.

We burned out the drives with a 800Mb/s sustained 24/7 write stream. In post-
mortem I did the math and the consumer drives ran out of endurance in less
than a month. We replaced the drives with enterprise drives which were
expected to last at least 3 years.

Also, here's a really strange finding... TRIM doesn't matter as much as one
would expect. Many TRIM implementations are buggy. If the SSD contains a
reliable TRIM implementation, then you can 100% guarantee that it will also
have internal "move stable bits around to level out the usage" code.

