
SSDs lose data if left without power for just 7 days - pyabo
http://www.ibtimes.co.uk/ssds-lose-data-if-left-without-power-just-7-days-1500402
======
baruch
The paper took something out of context, didn't really understand what it
reads and published nonsense.

The original blog post linked from the article is
[https://blog.korelogic.com/blog/2015/03/24#ssds-evidence-
sto...](https://blog.korelogic.com/blog/2015/03/24#ssds-evidence-storage-
issues)

It actually raises a point for a specific use-case, when a computer with an
SSD is taken for analysis (f.ex. a court case as evidence by the police) the
SSD is kept powered off and may lose its data and thus be worthless as
evidence after some time if the system is not kept in a normal temperature
(around 25C).

It's not a normal use-case and in fact it may be to the benefit of the user to
use an SSD in that case in the hope that the data will self-destruct with
complete plausible deniability.

------
dogma1138
What a bunch of nonsense... Here is the presentation:
[http://www.jedec.org/sites/default/files/Alvin_Cox%20%5BComp...](http://www.jedec.org/sites/default/files/Alvin_Cox%20%5BCompatibility%20Mode%5D_0.pdf)

All what they found is that there's a correlation between load, the operation
temperature during which data was stored, and the ambient temperature in which
the device is kept while switched off. This means that at an active
operational temperature of about 40c (which is normal for most consumer
drives) and a storage temperature of 30c (which is pretty much the upper
maximum of storage temperatures under residential conditions) your drive will
retain data for at least 52 weeks.

~~~
JoshTriplett
> and a storage temperature of 30c (which is pretty much the upper maximum of
> storage temperatures under residential conditions)

That might be a normal storage temperature, but it certainly doesn't seem like
a maximum. For instance, during the summer, an attic or similar unconditioned
enclosed storage area can easily exceed 40C during the day.

> your drive will retain data for at least 52 weeks.

That seems far too short. I'd like to see similar data for mechanical drives
and USB disks, but given the way flash storage works, I'm surprised that the
powered-off lifetime is that short; I'd have expected decades. I'm curious
what the actual failure mode is; what physically happens to the drive to make
it lose data?

I also find the charts in that presentation interesting: data retention really
_increases_ when storing data at a higher temperature? So for data retention,
it's better for the drive to run _hot_?

~~~
baruch
The spec is for the worst performance possible at end-of-life time. So a new
drive will retain the data far longer than 3 months or 1 year of the spec
(enterprise vs consumer spec) but a drive after five years of full writes will
retain for near-spec or it will be considered a failure and you can ask for a
refund.

The failure mode is that there are only about 50 electrons in that charge trap
of NAND flash these days and they can disappear on their own and they will
disappear after enough time and when they do you don't have the voltage you
should have and so can't read the bit value you stored in it. After enough
such bits become incorrect you can no longer fix the block with the ECC and
then you no longer have the ability to read the original data.

It should be noted that the more worn out the drive is the easier it is for
the electrons to disappear from the cell. Which is why a new drive retains
data perfectly well but an old drive can barely hold itself.

------
dne
Someone missed an important part of the standard (JEDEC JESD218, section 6.3):
"This standard is based on a use scenario in which the SSDs are actively used
for some period of time during which the SSDs are written to their endurance
ratings, followed by a power-down time period in which data must be retained."

E.g. in Intel's product spec for the DC S3500 series, the data retention
parameter is specified as: "3 months power-off retention once SSD reaches
rated write endurance at 40 °C".

------
JohnBooty

      According to a recent presentation by Seagate's Alvin
      Cox, who is also chairman of the Joint Electron Device 
      Engineering Council (JEDEC), the period of time that data 
      will be retained on an SSD is halved for every 5 degrees 
      Celsius (9 degrees Fahrenheit) rise in temperature in the 
      area where the SSD is stored.
    

"SSDs scary," says leading manufacturer of mechanical hard drives. "Mechanical
drives good! SSDs baaaaaad! You like good, yes?" he added.

~~~
creshal
Seagate is also a manufacturer of SSDs…

~~~
dogma1138
Seagate only recently bought a NAND supplier, all the mechanical disk
companies have major issues these days because they were too late for the SSD
game. They thought that they could improve both the density of the storage and
the performance before SSD's could catch up on the former and drastically
surpass them on the latter.

In the "early" days of SSD's they didn't offered that much better performance
especially in the enterprise storage arena than highend SAS/FC drives.

Both with improvements in controllers, the development of dedicated protocols
for SSD drives and the usage of a cheaper alternatives to FC in the form of
PCIexpress coupled with ever increasing storage density even in the enterprise
market SSD's are pretty much setup to take the entire storage market.

In consumer grade computing you only see mechanical disks in entry level
notebooks ("SSHD's usually with 16-32GB of SSD storage for OS and Cache"), for
for home network attached storage. 1TB consumer SSD's already can be bought
under the 400$ mark, and the closest mechanical drives with the same capacity
in terms of performance (still quite below the SSD) which are the
"professional grade" 10-15K RPM drives cost about the same. It's probably just
a question of 2-3 years before mechanical drives will be almost completely
written off the market, they already don't make much sense for enterprise
storage since they provide a cheaper alternative to high performance storage
even before you count the savings on electricity and cooling, and soon they
wont make sense for everyday consumers either.

------
thrownaway2424
Terrible article. The actual presentation in question is at [1]. The
presentation has nothing to do with performance in the field. Instead the
presentation is regarding JEDEC requirements, for which the relevant
specification is that "enterprise" class SSDs must retain their data when
powered off at 40C for 3 months.

1:
[http://www.jedec.org/sites/default/files/Alvin_Cox%20%5BComp...](http://www.jedec.org/sites/default/files/Alvin_Cox%20%5BCompatibility%20Mode%5D_0.pdf)

------
lectrick
I assume 7 days is worst-case scenario, corporate-level drive quality (which
is lower than consumer-grade) plus high temperature?

Is it becoming necessary to switch to a filesystem that ensures data integrity
with redundancy and regular checksums?

~~~
dogma1138
most corporate level SSD's are actually better than entry level consumer ones.

~~~
lectrick
Not according to the article :O

I presume it is assumed that corporate policy has better data integrity best
practices than your average Joe Homeowner.

~~~
dogma1138
Read the presentation this was the load testing for the Enterprise test, it's
pretty much a torture test with 100% load time.

With this I'm actually surprised that the SSD's lasted as much as they did,
for about 6 years now I've been using SSD's and the longest one of them
survived so far is less than 18 months, and at much lower loads than what
they've tested in. Since late 2008 I've been always running 2 SSD's for my
main system drive in raid 0 with no much load on them other than games, some
work stuff and the OS. At any point in which the drive has no more spare
blocks to relocate failed blocks too i toss it away and replace it (if read
errors come close to critical i do the same). For the first couple of years
the SSD's only lasted for about a year(my first Intel pair lasted something
like 5 months, but those were shitty controllers), this time with the Samsung
840 EVO's i have a feeling that they might actually last the whole 2 year span
of my desktop.

------
hundunpao
this is a joke right?

------
irrigation
This terrible article is actually a great example of a submarine. Note the
mention of a completely irrelevant "security" company halfway down, and then a
link to their blog post.

In any case, it's terrible because it takes testing criteria under extreme
conditions (don't store your SSDs at 55C) and then fearmongers this as the
norm.

~~~
snissn
submarine?

~~~
_wdh
It's a reference to a PG essay where he talks about how PR agencies often give
press releases and news stories that are little more than hidden adverts by
reporting selective truths:
[http://www.paulgraham.com/submarine.html](http://www.paulgraham.com/submarine.html)

~~~
Brakenshire
Sounds similar to the 'churnalism' concept.

[https://en.m.wikipedia.org/wiki/Churnalism](https://en.m.wikipedia.org/wiki/Churnalism)

