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<font face="Arial, Helvetica">I taught at Lanier Tech for a while as an
adjunct instructor. The computers there are kept in an
electronically frozen (not locked up) state so the students cannot make
any changes to them. If something is messed up, you just
reboot. Therefore, they cannot store any permanent work on
them. For that, they use memory sticks. I always encouraged
them never to rely on a memory stick as their only storage for their
work. I've seen a few times when the data just vanished or was
corrupted. The cells in a flash memory device have a limited number
of read / write cycles that they will tolerate. After that, they
fail to function. If, for example, you set a memory stick to be
your temp swap file, you'd probably burn it up quickly. <br><br>
From Wikipedia --><br><br>
<a href="http://en.wikipedia.org/wiki/Flash_memory" eudora="autourl">http://en.wikipedia.org/wiki/Flash_memory</a><br><br>
The write endurance of SLC Floating Gate NOR flash is typically equal or
greater than that of NAND flash, while MLC NOR & NAND Flash have
similar Endurance capabilities. Example Endurance cycle ratings listed in
datasheets for NAND and NOR Flash are provided.<br><br>
* SLC NAND Flash is typically rated at about 100K
cycles (Samsung OneNAND KFW4G16Q2M)<br>
* MLC NAND Flash is typically rated at about 5K-10K
cycles (Samsung K9G8G08U0M)<br>
* SLC Floating Gate NOR Flash has typical Endurance
rating of 100K to 1,000K cycles (Numonyx M58BW 100K; Spansion S29CD016J
1000K)<br>
* MLC Floating Gate NOR Flash has typical Endurance
rating of 100K cycles (Numonyx J3 Flash)<br><br>
<--<br><br>
Some flash memory, usually more expensive ones, use wear leveling
techniques to spread the writes over lots of cells and improve the
average life of the device. Since you never know which cells /
sectors you're really writing to, I don't know if there is even a way to
test a memory stick to verify it's integrity the way you could with a
HDD. Some also use spare sectors to write to when parts of the unit
fail. There are also two fundamental cell types, SLC and MLC.
This is getting beyond my level of expertise, but based on what I've read
and heard, SLC stores one bit of information in each cell by storing one
level of charge. MLC stores multiple bits of information per cell
by storing various levels of charge. They can be also configured as
NAND or NOR. MLC is cheaper and less reliable. SLC is more
expensive and more reliable. So, the really cheap memory stick you
get at the store may be the least reliable of all. Note that the
MLC NAND item above will only tolerate 5K - 10K cycles, versus 100K -
1000K cycles for the best ones.<br><br>
So, as Wolf said, life expectancy is questionable, but what's worse, it
varies by the construction of the device, and the usage pattern.
Depending on the application, device life could be much less than 5
years. I do believe reading the data is non destructive to the
device, but I'm not sure.<br><br>
For what it's worth, I just had a personal experience which may be
related to a flash memory failure. I have a portable MP3 player
that I listen to technical podcasts on. I have hundreds of files on
it. I listen to them, then erase them, and load new ones. I
recently was listening to a podcast, and all of a sudden, it began
playing audio from another unrelated podcast, but the screen said it was
still playing the same file. I've confirmed that the original
source file on my computer is valid, so I suspect data corruption in the
flash file. If this were a HDD, I'd use Spinrite to do a read /
write integrity test on every sector. I don't even know if that's
possible on a flash memory card. I guess I'll just erase the file
and reload it.<br><br>
By the way, in my opinion, the jury is still out on the longevity of SSD
"Hard Drives". I may own one some day, but I still plan
to have backups on spinning platters, for now. If you're storing
important data on a memory stick, I'd certainly want a duplicate
elsewhere, and if that duplicate is on another memory stick, I'd be
inclined to test the files periodically and refresh them, money
permitting of course.<br><br>
Steve Gibson has periodically talked about flash memory on the Security
Now podcast. You might try this search on Google:<br><br>
"flash memory" site:grc.com<br><br>
PS - My parents periodically take their photo memory card to Walmart,
plug it into the kiosk, and have a Photo CD made. I have no idea
what that costs. Also, something like Jungledisk or Carbonite might
be a great way to make sure those photos are backed up online. I
use Jungledisk. The cost is $ 0.15 / GB / Mo. for storage.
When you send or receive data, there is a bandwidth fee of something like
$ 0.18 / GB, and a $ 3 / Mo. maintenance fee I believe. If most of
your files are archival and don't change much, the cost is not too
high. There is a premium option which only uploads the changed
parts of updated files for an extra $ 1 / mo, I believe. I don't
know about the cost structure of Carbonite.<br><br>
Sincerely,<br><br>
Ron<br><br>
At 10/4/2010 06:48 AM -0400, Wolf wrote:<br>
<blockquote type=cite class=cite cite>Even the best CDR-W have about a
2-year life expectancy<br>
Paper is by far the most time-resistant media for photos. <br>
Ansel Adams Photos still exist. (They always looked that weird)<br><br>
Do you want to start talking about the relative friability of
media?<br>
flash memory has about a max life of 5 years unless the stick or <br>
SHD is powered up at regular intervals. (I am not sure of the
interval)<br><br>
-Wolf<br><br>
<br>
-----Original Message-----<br>
<b>From</b>: Paul Cartwright
<<a href="mailto:Paul%20Cartwright%20%3cale@pcartwright.com%3e">ale@pcartwright.com</a>><br>
<b>Reply-to</b>: Atlanta Linux Enthusiasts - Yes! We run Linux!
<ale@ale.org><br>
<b>To</b>: Atlanta Linux Enthusiasts - Yes! We run Linux!
<<a href="mailto:Atlanta%20Linux%20Enthusiasts%20-%20Yes!%20We%20run%20Linux!%20%3cale@ale.org%3e">ale@ale.org</a>><br>
<b>Subject</b>: [ale] OT- Re: Cd-r life<br>
<b>Date</b>: Sun, 3 Oct 2010 06:46:52 -0400<br><br>
<br>
</font><pre><font face="Arial, Helvetica">
On Sat October 2 2010, Ron Frazier wrote:
> TDK had a similar product at one time, but I couldn't find it on
their
> website now. Here's the link to their storage media
website. Look for the
> word archival in the name, but be sure to check the specs.
Some discs are
> just a heavy duty scratch resistant standard discs.
>
>
<a href="http://www.tdkperformance.com/en-us/Storage-Media/">http://www.tdkperformance.com/en-us/Storage-Media/</a>
ok, since we are now talking photos & not linux, it becomes OT:)
the problem with the photoarchival TDK CDs is, it now takes me 2 DVDs to
store
my photos, and that size grows almost daily:) I now use at least 1 USB
stick
to store photos on. As soon as I get A JOB, I will get a bigger USB
stick,
and eventually multiple sticks, just for my photos..
</font></blockquote><br>
<br>
<div>--------------------------</div>
<div>(PS - If you email me and don't get a quick response, you might want
to call on the phone. I get about 300 emails per day from alternate
energy mailing lists and such. I don't always see new messages very
quickly.)</div>
<br>
<div>Ron Frazier</div>
<br>
<div>770-205-9422 (O) Leave a message.</div>
<div>linuxdude AT c3energy.com</div>
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