On Fri, 28 Oct 2016 21:03, Alessandro Baggi <alessandro.baggi@...> wrote:
Hi Yamaban,
Great expalanation. I think you know how to buy an ssd. There is no doubt
about samsung ssds quality vs other. My question about neutron was to get
your opinion about this product.
My doubt was about differences between slc, mlc and tlc. Mlc endurance
respect tlc is better and I though that the mlc of neutron gives me more
endurance respect to the tlc. From a technic point of view, why the samsung
tlc is better of corsair mlc? And what about v nand? Have you used it?
Thanks in advances
[snip]
Hi Alessandro,
For the clear picture, if I'm talking about "Corsair SSD" I mean the
"Corsair Neutron XTi", because the "Corsair Force LE" is pretty much a
no-go for anyone that has to rely on the data stored for more than 3 years
at a work load of 9 hours per day / 5 days a week / 50 weeks a year
(ca 2250 hours per year) at ca 8TBW written per year.
I'm not take these numbers out of the air, but that is what an normal
office PC is based on. Those 8TBW per year come from observation on
Microsoft Windows 10 Profesional and latest Microsoft Office Professional
and include nearly half system / half user caused writes on average per
year. Those Microsoft updates and shadow-copies are much more heavy
than most people thought.
Thankfully most Linux-Distros cause a much lighter system part of the
Write load of the drive than Windows, but COW based file-systems
like btrfs are on the uptake and that will rise the write load.
Now, on Flash Technology. Hmm.
I've started on that with UV-Erasible E-Prom in 1987 (100 Erase cycles),
went on with EE-Prom (over 10.000 Erase cycles!, but only 10 years data
retention), and near 1990 Flash-EEProm (Block-wise erasible) became
available at prices a student could pay from his/her spending money
The writes on early Flash where painfully slow, about 1% of the
read-speed, at the beginning. the more wide-spread usage
(in digital still-cameras and mobile phones) brought a (slow)
change to more write speed, but at what cost? Data Retention Time!
[... long rant removed, its late in the (not so pleasan)t day ...]
On the difference of nand and v-nand: "normal" nand uses "floating gate"
while v-nand aka "vertical-nand" uses a "charge trap" (capacitor) to store
the bit information.
The Wikipedia article on Flash gives some more indepth info:
Flash : https://en.wikipedia.org/wiki/Flash_memory
MLC/TLC: https://en.wikipedia.org/wiki/Multi-level_cell
Conclusion: a well produced (first class / datacenter class) TLC Nand
is very similar to a middle class MLC V-Nand, both in terms of access
speed and write endurance.
But the MLC will be at least 10% bigger on the die.
ATM, it is a cost balance between a lower yield on high quality smaller
TLC, and higher yield middle class bigger MLC
So, for the End user wheter "MLC V-nand" or "TLC nand" is much less
interresting than the question of "how well does the manufacturer
understand the used flash and how well was the controller adapted to it"
Corsair as a SSD manufacturer buys both, the flash, and the controller,
from other manufacturers, while Samsung does it completely in-house.
Thus it is not surprising that Corsair does still use the MLC technology
while Samsung has already made the step to TLC.
I see that as a unspoken statement from Corsair that "we do not have to
knowlegde avaliable (atm.) to make a TLC drive of the same quality than
a MLC one." That is not negative in any way. A manufacturer that knows
his limits is much better than one that jumps on a new hype with to
little knowlegde.
Samsung is very careful about its promises on write endurance.
TLC is still a young technology and that shows in lower TBW,
so the warranty says for the "Evo" says:
"5 years or TBW per spec, what ever is reached first".
That's honesty in my eyes.
If the question would be the "Samsung 850 EVO" with MLC Flash from last
year, or the new "Corsair Neutron XTi" there would be little to no
difference in TBW, but the price of the Samsung was ca 10% higher.
IIRC, the TBW spec from you old 120GiB Corsair was below 10TBW, and you
are nearly on the 7TBW mark after 5 years, even the 75TBW of the 250GiB
Samsung should hold out for the next 5 years.
My baseline is: wether the "Samsung 850 EVO" with TLC or the
"Corsair Neutron XTi" with MLC, is more a matter of gut-feeling
than anything else. As you will not buy the SSD in packs of 20 or more
you never get into any discount scheme, so that offer from Samsung
will also not matter in any way, and at the point where you buy it,
the price per GiB will be nearly equal. Both offer 5 years warranty.
Have a nice weekend
- Yamaban
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