On Mon, 23 Jul 2012 08:46:21 -0400, "Arny Krueger"
wrote:
"Mxsmanic" wrote in message
news
Just out of curiosity, have you ever actually experienced a memory card
failure due to simple wear and tear?
You are talking about a moving target because the life of flash memory
continues to increase. It was on the order of thousands of erase/write
operations a few years back, and now it is on the order of 100'000s.
According to Wikipedia:
a.. SLC NAND flash is typically rated at about 100k cycles (Samsung
OneNAND KFW4G16Q2M)
b.. MLC NAND flash used to be rated at about 5-10k cycles (Samsung
K9G8G08U0M) but is now typically 1k - 3k cycles
c.. TLC NAND flash is typically rated at about 100-500 cycles
d.. SLC floating-gate NOR flash has typical endurance rating of 100k to 1M
cycles (Numonyx M58BW 100k; Spansion S29CD016J 1,000k)
e.. MLC floating-gate NOR flash has typical endurance rating of 100k
cycles (Numonyx J3 flash)
I know that flash memory allows for only a limited number of write cycles,
but
I'm curious as to how often this limit has actually affected people in
real
life.
I currently have 4 flash-based SSDs in service. None are being hit
particularly hard. IOW they are not parts of highly active file servers.
They are typically in computers that only receive a few hours of use per
week.
I've never experienced a memory-card failure of any kind [knocking on
wood],
Lucky you! But, all of the failures I've seen were of conventional system
RAM.
and hopefully I never will, although a simple inability to write to the
card
would probably be less of a disaster than an inability to read what's
written
(apparently wear and tear only impedes writing, but reading still works).
I
always have several cards with me at least, and I try to cycle through
them to
even out the wear and tear. I've been lucky so far.
IME writing, while time consuming is not the big exposure.
The trick of the day often relates to reading the data later on. Memory
write cycles seems to have nothing to do with it. It's all about the USB
interfaces.
I just had a client who needed to restore some backups after a total loss
type hard drive crash. His USB flash drive had about 9 GB of data. It
blue-screened the laptop its data needed to be restored to after a few
minutes of loading. Its reliability for just reading was poor on 3 other
desktop systems. The drive disconnected itself from the system several times
during attempts at restoring it, and on one machine that normally works
well, it would just sit in a loop attaching, crashing, and re-attaching. On
another older laptop the whole 9 GB flowed to its hard drive (a flash-based
SSD) just fine in one clean shot. I moved the data to the target machine
over a wireless LAN without incident.
YMMV.
I just ha
I've seen the interface chip in thumb drives short and smoke. Chuck