Flash memory vs. hard disk

[flarosa]

How fast are the fastest flash memory devices these days? Do they
compare to the speed of a hard drive?

I'm wondering if doing something like installing a 4MB Compactflash
card in my laptop via a PCMCIA adapter or a USB 2.0 adapter and using
it as the Windows swap file, the temp directory, or some other similar
purpose, will do me any good in terms of speed.

Thanks,
Frank

 

[kony]

How fast are the fastest flash memory devices these days? Do they
compare to the speed of a hard drive?

Depends on exact access, and interface (bus). Yes in some
ways they compare, but it depends even more exactly what
you're doing. For general purpose OS use, it will be slower
unless you pay a premium for a new integrated flash drive,
hard drive replacement type of product.

I'm wondering if doing something like installing a 4MB Compactflash
card in my laptop via a PCMCIA adapter or a USB 2.0 adapter and using
it as the Windows swap file, the temp directory, or some other similar
purpose, will do me any good in terms of speed.

Doubtful, or at least not enough of a difference to matter.
I assume you mean 4GB not 4MB, and would think that a nice
way to transport data back and forth, keep a copy of
imporant data safe w/you instead of in the laptop where it's
more prone to be stolen.

 

[Vanguard]

How fast are the fastest flash memory devices these days? Do they
compare to the speed of a hard drive?

I'm wondering if doing something like installing a 4MB Compactflash
card in my laptop via a PCMCIA adapter or a USB 2.0 adapter and using
it as the Windows swap file, the temp directory, or some other similar
purpose, will do me any good in terms of speed.

Thanks,
Frank

You are going to use a 4MB flash card for temp, paging, or "other
similar purpose" when the hard drive is multi gigibytes in size? (rolls
eyes) Maybe you meant a 4GB flash card. Still way too small
considering you probably have a 100GB drive, or larger.

Flash media is not anywhere as reliable as hard drives. It literally
wears out over time and continued use. If you used it, say, as pagefile
or temp space, they get exercised a lot and nearly continuously so it
wouldn't be long before you consume those million cycles of use per bit,
and it is likely the lower addressed bits get exercised more often.
Talk to anyone that has owned a digital camera for awhile. Everyone I
know with one has their story to tell about flash cards that stop
working and they get stuck having to buy another. In fact, most take a
spare card with them on vacation because they know they go bad.

From another of my posts found via Google Groups search:

Don't be misled that electronics are infallible. Just because a USB
thumb drive uses flash memory doesn't mean it won't wear out. They can
endure a maximum number of writes or erases. Flash memory can only be
flashed so many times (i.e., although electronic, they wear). How often
have you written files (or deleted them or done anything to update the
flash drive)? If you are using a program that updates its files on the
flash drive, remember that all those updates count against the endurance
of the device. Some apps could make a several thousand updates per
minute and do so as long as the app is running. Write/erase endurance
specs are usually hard to find and rarely divulged by the device makers
(so you have to read articles by the flash memory manufacturers). Also,
memory does go bad, whether it be in a flash drive or your system RAM.
If you own a digital camera for a couple years, you will experience
having to toss away their flash cards when (not if) they fail.

"Like all flash memory devices, flash drives can sustain only a limited
number of write/erase cycles before failure. In normal use, mid-range
flash drives currently on the market will support several million
cycles, although write operations will gradually slow as the device
ages." (http://en.wikipedia.org/wiki/Keydrive). "Flash memory has a
finite number of erase-write cycles (most commercially available flash
products are guaranteed to withstand 1 million programming cycles) so
that care has to be taken when moving hard-drive based applications"
(http://en.wikipedia.org/wiki/Flash_memory). Flash drives should NOT be
used for permanent storage and any files placed on it should be
non-critical files (i.e., you can afford to lose them the same day you
put them onto the flash drive). Just like with a hard drive, anything
you put onto a flash drive - if important to you - should be backed up
to provide a second copy (because MTBF for the two drives is not linear
so your chances of having the file is highly increased by having a
backup). Flash drives are less prone to physical abuse than hard
drives, but then your hard drive, after installed, receives little
physical abuse whereas you are subjecting the flash drive to static,
dirt, wear from insertion/extraction, shock, and other environmental
factors. Unlike your system or video RAM, flash memory does wear out as
it suffers from electric field stress (thin oxide stress). "Over time,
oxide stress from repeated program and erase operations may degrade the
gate oxide layer to cause the transistor to malfunction. This
contributes to faulty operation of the flash memory device. Accordingly,
there is a need for a method of detecting a transistor error caused by
the degradation of the gate oxide layer "
(http://www.freshpatents.com/Flash-memory-device-capable-of-reducing-t...)
and that is why some of these devices will incorporate fault-tolerant
schemes to mask the failures.

 

[kony]

You are going to use a 4MB flash card for temp, paging, or "other
similar purpose" when the hard drive is multi gigibytes in size? (rolls
eyes) Maybe you meant a 4GB flash card. Still way too small
considering you probably have a 100GB drive, or larger.

Flash media is not anywhere as reliable as hard drives. It literally
wears out over time and continued use. If you used it, say, as pagefile
or temp space, they get exercised a lot and nearly continuously so it
wouldn't be long before you consume those million cycles of use per bit,
and it is likely the lower addressed bits get exercised more often.
Talk to anyone that has owned a digital camera for awhile. Everyone I
know with one has their story to tell about flash cards that stop
working and they get stuck having to buy another. In fact, most take a
spare card with them on vacation because they know they go bad.

I would tend to very strongly disagree with this. Flash
cards are far far far far far far far more reliable than
hard drives. It may be the case that a poor host device
scrambles one, but a flash card can be ran over with a car,
put through the washing machine, soaked in your coffee every
morning, and survive most events that would kill the person
using the device and destroy the device itself.

Yes they have write cycle limitations. That's why this type
of use is best with a card several times larger than the
datastore on it, because that directly bears on total write
cycles available. It might not be so great for a pagefile
but for just about any other use that's a lesser fraction of
total drive capacity, it would be years before the card
wore out, and quite reliable until that happens.

From another of my posts found via Google Groups search:

Don't be misled that electronics are infallible.

Never was, but when it comes to data storage, flash memory
is an order of magnitude closer to infallible than anything
else.

Just because a USB
thumb drive uses flash memory doesn't mean it won't wear out.

Which does not bear against it being extremely reliable up
until the point when it does wear out. It is not a reason
to avoid flash, it is a reason not to use the same flash
device for anything important for several years or any
extremely high write cycle activity.

They can
endure a maximum number of writes or erases. Flash memory can only be
flashed so many times (i.e., although electronic, they wear). How often
have you written files (or deleted them or done anything to update the
flash drive)? If you are using a program that updates its files on the
flash drive, remember that all those updates count against the endurance
of the device. Some apps could make a several thousand updates per
minute

"could"? Name some.
You are trying very hard to stretch a point, probably until
it doesn't come close to the real-world situations in which
people do use flash fine.

and do so as long as the app is running. Write/erase endurance
specs are usually hard to find and rarely divulged by the device makers
(so you have to read articles by the flash memory manufacturers).

I agree this is one area in which one has to do more
research, BUT isn't that what anyone does before
implementing a flash device in an unusual way? At least we
can say they should, just like they would do the research
before deploying any technology product they are unfamiliar
with.

Also,
memory does go bad, whether it be in a flash drive or your system RAM.
If you own a digital camera for a couple years, you will experience
having to toss away their flash cards when (not if) they fail.

I've owned my present camera for over two years, not one
single flash card has been thrown away. Not one loss of
data. One of the SD cards is even in a multi-in-one card
reader which a system boots and runs Win2k. Flawlessly.

If you find certain devices are losing data on flash cards
within a couple years, steer clear of them (the device) like
the plague as it is not the flash card in almost any case.
It's possible 1 card in thousands are defective, but so it
is with any product that doesn't undergo continual testing
and very expensive QC.

"Like all flash memory devices, flash drives can sustain only a limited
number of write/erase cycles before failure.

And extremely reliable during that time.

Flash drives are less prone to physical abuse than hard
drives, but then your hard drive, after installed, receives little
physical abuse whereas you are subjecting the flash drive to static,
dirt, wear from insertion/extraction, shock, and other environmental
factors. Unlike your system or video RAM, flash memory does wear out as
it suffers from electric field stress (thin oxide stress). "Over time,
oxide stress from repeated program and erase operations may degrade the
gate oxide layer to cause the transistor to malfunction. This
contributes to faulty operation of the flash memory device. Accordingly,
there is a need for a method of detecting a transistor error caused by
the degradation of the gate oxide layer "
(http://www.freshpatents.com/Flash-memory-device-capable-of-reducing-t...)
and that is why some of these devices will incorporate fault-tolerant
schemes to mask the failures.

These kinds of failures from abuse are no knock against
flash, if you wanted to keep one safe-n-sound in a system
like you would a hard drive, you can.

If you want to take a hard drive and bang it around, drop it
in a pond then try to use it, go right ahead and then
compare it to flash.

Claims of degradation are factored for in the lifespan
ratings.

There is nothing even remotely close to as reliable as flash
memory, used in the same scenarios as anything else with one
exception that you've stretched beyond reason - that it
would not be chosen for extremely high write cycle scenarios
or it would be replaced more often in those scenarios.

That doesn't mean one can ignore the other factors though, a
poor quality card reader or device, or a user that subjects
a product to ESD, is not a fault of the device. Show us a
hard drive that likes ESD or dodgy cabling.

 

[Trimble]

@@@"Do they compare to the speed of a hard drive?."@@@

Not well..half the speed at very best..even of a slow LapTop type.
Beware the available USB Flash speeds vary enormously..
from 5 Mbs to 25 Mbs ..there are a few around at 35 mbs .
They are often speed quoted by comparison to CD speeds e.g. x50 ...x130 (at
best).

They will not provide a sensible alternative to a H.D .Its almost impossible
to
Boot directly from one of them so they can't even be regarded as
alternatives to Floppy's
& are best used for easy move-around storage.
The ReadyBoost feature in VISTA can be useful on a slower LapTop .
(\__/)
(='.'=)
(")_(") Mouse

 

[kony]

@@@"Do they compare to the speed of a hard drive?."@@@

Not well..half the speed at very best..even of a slow LapTop type.
Beware the available USB Flash speeds vary enormously..
from 5 Mbs to 25 Mbs ..there are a few around at 35 mbs .
They are often speed quoted by comparison to CD speeds e.g. x50 ...x130 (at
best).

They will not provide a sensible alternative to a H.D .Its almost impossible
to
Boot directly from one of them so they can't even be regarded as
alternatives to Floppy's

? Almost impossible to find a board that can't boot
directly from one, if you select the right flash device for
the era of board.

Many (if not most) motherboards can now boot a USB
thumbdrive. A lot of those can also boot many multi-card
readers with your choice of media in it. ANY of them, the
vast majority and probably every last PATA/IDE boad made for
over a dozen years can boot a Compact Flash card with a $4
CF-IDE adapter.

 

[Vanguard]

http://www.datarescue.com/laboratory/cfcompare/index.htm


I belong to the local Disney club. We meet one or two Saturdays a
month. I go to Disney 3 or 4 times per year and each time I take the
digital camera. Because of the water rides, sweat, crowds, and
handling, I've gone through several digital cameras. I've also gone
through several flash cards for each because they went dead. There
isn't anyone in the Disney club that doesn't take spare cards simply
because they all know they will probably lose one on a trip (lose as in
it dies, not that they misplace the card or it gets stolen). Good for
you that your cards have survived your handling and use of them. That
viewpoint doesn't seem prevalent in my realm of friends using them.

The fault tolerant (or wear leveling) algorithms are to mask failures
until they exceed the ability to be masked. As masking increases,
capacity decreases. Also, flash memory slows over time (but is still
probably more than fast enough for its *intended* use). The controller
in the flash card tries to level the wear by spreading out the remapping
so, as you say, the device dies suddenly rather than becomes crippled
and perhaps unusable because just one area is overly worn. See
http://www.storagesearch.com/siliconsys-art1.html.

As for using the flash card as, say, temp file space, a million or two
or three programming cycles sounds real high until you realize how often
files are rewritten in this temp space. I've seen anti-virus products
write to a file in temp space at 2900 writes accesses per minute (I was
checking at the time why EzAntivirus and Prevx seem to get into a
thrashing mode with each other on the same files). After 6 hours,
there's a million writes. Hopefully the silicon-based controller on the
flash card works its remapping wonders so wear leveling gradually moves
all those writes to less worn blocks but then most folks want to use
their computer more than 6 hours, 6 days, 6 weeks, and maybe even up to
6 years. Obviously this situation isn't normal. The user could use
Filemon from SysInternals to see how often they are making writes into
the temp space in which they want to employ a flash card. Don't know
which hard drives you or the OP buy but mine usually last more than 5
years. I don't think a flash card will make it past several months but
that's just a guess and based on the death rate that I've experienced.
Maybe you've been luckier than our Disney group of shutterbugs.

That's not to say silcon disks aren't far better than mechanical hard
drives. SSDs are far better - at a hefty price - than are hard drives.
See http://www.storagesearch.com/bitmicro-art3.html. But these are
SSDs, not flash cards.

 

[kony]

http://www.datarescue.com/laboratory/cfcompare/index.htm


I belong to the local Disney club. We meet one or two Saturdays a
month. I go to Disney 3 or 4 times per year and each time I take the
digital camera. Because of the water rides, sweat, crowds, and
handling, I've gone through several digital cameras. I've also gone
through several flash cards for each because they went dead. There
isn't anyone in the Disney club that doesn't take spare cards simply
because they all know they will probably lose one on a trip (lose as in
it dies, not that they misplace the card or it gets stolen). Good for
you that your cards have survived your handling and use of them. That
viewpoint doesn't seem prevalent in my realm of friends using them.

Ok, but consider the vast number of people using flash in
cameras and other devices these days, I think we can see the
problem is not very common at all, there are insufficient
reports of it compared to the user base.

The fault tolerant (or wear leveling) algorithms are to mask failures
until they exceed the ability to be masked. As masking increases,
capacity decreases. Also, flash memory slows over time (but is still
probably more than fast enough for its *intended* use). The controller
in the flash card tries to level the wear by spreading out the remapping
so, as you say, the device dies suddenly rather than becomes crippled
and perhaps unusable because just one area is overly worn. See
http://www.storagesearch.com/siliconsys-art1.html.

As for using the flash card as, say, temp file space, a million or two
or three programming cycles sounds real high until you realize how often
files are rewritten in this temp space.

Here I disagree, a million or two IS really high when you
factor for the card being multiple times as large as the
temp files so it's a million * % of capacity. Even so, I
never suggested flash primarily for use as temp file space.

I've seen anti-virus products
write to a file in temp space at 2900 writes accesses per minute (I was
checking at the time why EzAntivirus and Prevx seem to get into a
thrashing mode with each other on the same files).

Abandon them, there is no excuse for that kind of excess in
this day and age. Your point is valid but it resides
within the context that the storage device be chosen for the
use, not just randomly selecting flash no matter what the
use is.

After 6 hours,
there's a million writes.

I suggest that nothing should be allowed to run like this
for 6 hours. Let's get back to a normal scenario instead of
extremes that aren't usually present. I have systems
running windows, an OS not known to be conservative about
writing to HDD, from CF cards. I did disable some logging
and paging, but for the specific application it works fine.
They are SLC cards not MLC. As with anything else when one
builds a system they have to consider the pros and cons of
each device.

Hopefully the silicon-based controller on the
flash card works its remapping wonders so wear leveling gradually moves
all those writes to less worn blocks but then most folks want to use
their computer more than 6 hours, 6 days, 6 weeks, and maybe even up to
6 years.

If we wanted to go to extremes we could kill any piece of
hardware with some hypothetical situation, but until such a
scenario is posed, it is unwarranted to make blanket
statements that only apply in atypical scenarios. While it
is important to recognize flash has a limited # of write
cycles, that does not prevent it from being viable for many
uses, and the failures your friends saw in their cameras
were certainly not failures from # of write cycles. The
number of people who are actually reporting failures in
certain areas due to excessive write cycles is quite low, an
unusual use.

Obviously this situation isn't normal. The user could use
Filemon from SysInternals to see how often they are making writes into
the temp space in which they want to employ a flash card.

Yes this is a very good suggestion, and one I used when
setting up windows on CF cards.

Don't know
which hard drives you or the OP buy but mine usually last more than 5
years. I don't think a flash card will make it past several months but
that's just a guess and based on the death rate that I've experienced.
Maybe you've been luckier than our Disney group of shutterbugs.

All my flash cards are between several months to years old.
None have write cycle failures. Their reliability has been
far better than HDDs.

That's not to say silcon disks aren't far better than mechanical hard
drives. SSDs are far better - at a hefty price - than are hard drives.
See http://www.storagesearch.com/bitmicro-art3.html. But these are
SSDs, not flash cards.

Actually no, there is no technical reason why a SSD is any
different when it comes to reliability or longevity,
actually the opposite, there are more mechanical aspects and
failure points to them, their lone saving grace is
threefold:

1) Significantly higher capacity increases odds of more
free space so there are fewer rewires per area per period.

2) Significantly higher odds it's SLC instead of MLC.

3) Hooked up to an ATA or SATA interface on a more
developed *system* and somewhat protected in that system,
not as subject to variables like handling or other factors
which would damage the system before the flash drive in it.

If you take a look at small mechanical hard drives in
devices like portable media players and cameras, they fare
worse than flash when it comes to reliability and
ruggedness. We could expect the same from larger notebook
sized HDDs as well, if their larger size didn't limit the
applications as much.

If you find a camera destroying flash cards, abandon the
camera, or look at the whole environment the card sees,
right this moment the newsgroup post I'm replying to was
read from a flash drive. It will most likely suffer the
same fate as the prior I'd used, it'll be replaced to
increase capacity, not because it had failed in any way.