How it is possible

Carlos E.R. wrote:
On 08/03/2021 00.30, J. P. Gilliver (John) wrote:
On Sun, 7 Mar 2021 at 16:12:25, micky wrote
(my responses usually follow points raised):
How it is possible that one SSD is 17 times as fast as another but costs
less? Both are 240G. Why would anyone buy the slower one (like I did
last summer)?
[]
In the comparison list of the first one, 4 of them side by side, half
way to the bottom of the page, 2 others are the same speed as the first,
but the second one is 17 times as fast.

In a similar side-by-side comparison list on the second page, the same
thing is true. Only the PNY is so fast, and for less money. Does PNY
know something the others don't know.

Even leaving aside Jeff's point about bits versus bytes, speed isn't
the only important parameter for and SSD: there are probably many, but
the one that bugs me is the tolerated number of writes - which for the
same size SSD in the same machine/use, more or less maps to lifetime.
You also need to know how they behave when they reach their end of
life: do they continue trying to work (I don't think any), switch to
read-only, or just become a brick (at least one make/range does).

Which one bricks? That's important to know.


Intel SSDs stop both reads and writes, when the wear life is exceeded.
Once the wear life hits, say, 3000 writes per location, the drive
stops responding. This makes it not possible to do a backup
or a clone.

As a consequence, the user is advised to keep a Toolkit handy
which has an end-of-life predictor, for better quality handoff.

Of course your drive is not near end of life. But, you
only know the wear rate, if you check the Toolkit occasionally
for the projections on life. And, you look pretty bad, if the
topic slips your mind, and you start asking for help with that
"too crusty backup I made two years ago". We don't want
this topic to be handled by people losing data.

It's a shame, that several of the toolkits, suck. I was
not impressed with a couple I checked. Hobbyists could
write better code - code that displayed the salient data
to keep users informed.

And a drive I could not keep because the hardware sucked,
the toolkit was great. That's just how this computer stuff works.

*******

The point of making an example out of Intel, is to make you
aware of what the most extreme policy is. And Intel wins the
prize in this case. Some products from competitors, will
allow you to read, and they stop writing. This allows you to
make a backup using a Macrium CD, and prepare a replacement SSD.

The reason Intel stops reading, is to guard against the possibility
that read errors are not getting detected properly. Intel arbitrarily
decided that only "perfect" data need apply. And they weren't going to
allow a certain BER to leak out and then customers blame Intel
for "accepting corrupt data".

One of the BER indicators in the SSD datasheets, is 10x less good
than a hard drive (one product might be 10^-15, the other 10^-14
kind of thing). And you may find review articles making
references to this, that this difference is a bad thing.

The ECC on SSDs is already a pretty heavy weight item. A bit
more than 10% of flash cells, are likely being used just to
hold the ECC. And it's that ECC calc that keeps TLC flash
from ruining our data. One of the first TLC drives, every
sector had errors, and it was the ECC that transparently
made the drive look "perfect" to the user. When this happens,
the drive can slow down (ECC done by ARM cores, not hardware),
and this makes the more aggressive storage techs (QLC flash)
look bad. It's the "stale slow" drive problem - one way to
fix it, is for the drive to re-write itself at intervals,
which of course depletes the wear life.

The topic is a lot like BEV (electric) cars :-) "Different,
in a bad way" :-) The populace will know, when everyone has
had the mechanic tell them "your battery pack needs to be
replaced".

Paul