USB memory pen lifespan test?

  • Thread starter Thread starter Robi
  • Start date Start date
R

Robi

Hi,
I wonder if someone knows about a serious discussion and/or article
about the lifespan of modern usb pendrive memories.

I am trying to get a realistic point of view about how those usb pen
could be used as everyday storage. I know well those memory devices do
have a more limited lifespan than traditional harddisks but I did not
find any good documentation about that, no numbers, no real-life
tests, no deep technical analisys, just theories and very few product
specific technical details.

Can someone point me to a good resource on the internet about all of
that?
Thanks,
Roberto
 
Robi said:
Hi,
I wonder if someone knows about a serious discussion and/or article
about the lifespan of modern usb pendrive memories.

I am trying to get a realistic point of view about how those usb pen
could be used as everyday storage. I know well those memory devices do
have a more limited lifespan than traditional harddisks but I did not
find any good documentation about that, no numbers, no real-life
tests, no deep technical analisys, just theories and very few product
specific technical details.

Can someone point me to a good resource on the internet about all of
that?
Thanks,
Roberto
Click to expand...
The math is pretty simple.
If you get 10,000 write cycles and write it once a day, you'll get
30 years out of it. Depending on what you write, load leveling can
make this much longer.
If you try to use it as swap space for an active OS that you're writing
every millisecond, it will last for 10 seconds. Again, load leveling
can dramatically increase this, but 1000 x 10 seconds still ain't very
long.
You can fuss over the numbers, but the
Botom line: good for storing stuff, bad for dynamic stuff.
mike
 
Previously Robi said:
Hi,
I wonder if someone knows about a serious discussion and/or article
about the lifespan of modern usb pendrive memories.
Click to expand...
I am trying to get a realistic point of view about how those usb pen
could be used as everyday storage. I know well those memory devices do
have a more limited lifespan than traditional harddisks but I did not
find any good documentation about that, no numbers, no real-life
tests, no deep technical analisys, just theories and very few product
specific technical details.
Click to expand...
Can someone point me to a good resource on the internet about all of
that?
Click to expand...

There is none. Sorry. The load-leveling methods are usually proprietary
(read: secret). For the Flash memory itself, there exists different
durability alternatives. At the very low end you get 100 overwrites.
That is mostly for some special purpose flash cells, as in GAL logic
chips. Typical flash memory can withstand 10'000...100'000 weite cycles.
With load leveling, error correction and defect management, this can
go up to million write cycles for a specific, high-load sector.

Arno
 
The math is pretty simple.
If you get 10,000 write cycles and write it once a day, you'll get
30 years out of it.
Click to expand...

Nonsense. 10,000*365*30=109,500,000

Now show me a flash device that has 100 million write cycles.
 
Missing said:
Nonsense. 10,000*365*30=109,500,000

Now show me a flash device that has 100 million write cycles.
Click to expand...

You should change your name from missing person to missing math skills.
Guess all that licking is distracting...
Accurate math?? yes! Right math???? no!
365 x 30 = 10950 write cycles, which ain't far from 10,000.
Pay attention!!!
 
mike said:
You should change your name from missing person to missing math skills.
Guess all that licking is distracting...
Accurate math?? yes! Right math???? no!
365 x 30 = 10950 write cycles, which ain't far from 10,000.
Pay attention!!!
Click to expand...

Not sure what a memory pen is. I have a Sony 2.0 128MB Microvault (a stick
drive?). Does the above write cycle limit apply to this as well? And to my
new WD USB 2.0 Passport 120GB Portable HDD, 5,400 rmp? :-(
--
With the below, I may be walking into a mine field. :)

Wouldn't the math be:
10,000 / 365 = 27.39 years? Assuming conservative one write a day.

Now that I'm aware of cycle limits, I'll write much less to the drives.

Thanks,
Dugie
 
Not sure what a memory pen is. I have a Sony 2.0 128MB Microvault (a stick
drive?). Does the above write cycle limit apply to this as well? And to my
new WD USB 2.0 Passport 120GB Portable HDD, 5,400 rmp? :-(
Click to expand...

The Sony yes, since it is an USB flash drive, the WD no. The latter is
a HDD, no limit on overwrites there. But the base-numbers are wrong
anyways.
Wouldn't the math be:
10,000 / 365 = 27.39 years? Assuming conservative one write a day.
Yes.

Now that I'm aware of cycle limits, I'll write much less to the drives.
Click to expand...

The limits are much higher. There are two types of Flash: NAND and
NOR. NAND is slower, but has > 100'000 write cycles per cell/sector.
In addition, good quality sticks perform load-leveling, were
writes to the same sector do not go the same sector. (Some high-load
sectors (FAT, e.g.) are written to in each write operation to a
partition, so this is important.) There may also be strategies to
recognize and replace defective sectors, e.g. additional bits
that allow some error correction amd when they are needed, the sector
is not used anymore. Much like HDDs do.

All in all you can expect something like > 10.000.000 write ops for a
good quality USB flash drive, possibly many more. Without exact
knowledge of the exact leveling strategy it is really impossible
to tell and the vendors are not talking. The german computer magazine
c't recently tried to break sime sticks by permanent writing, but
failed (don't remember details of the test.)

The real lifetime concerns arise for long-term storage (maybe only
about 10 years data durability on flash memory sticks) and when flash
memory replaces disk drives. With a conventional filesystem and
conventinal OS log-writing (can be serveral writes per minute), some
earlier flash drives failed withing months.

Arno
 
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