ToolPackinMama said:
Hmm, I didn't know that about SSD drives, can you elaborate?
Memory drives (like those USB thumb drives) incur oxide stress across their
transistor junctions. That is, they DO wear out. Masking algorithms are
included in the interface firmware to the device to correct for defective
blocks of memory: if a block of memory tests as bad, reserve memory is used.
The bad block is mapped to a reserve block. Eventually the reserve memory
gets used up and no more mapping is possible. That's when the memory drive
catastrophically fails. That's why it makes sense to use flash drives for
data storage because it doesn't undergo the extreme changes that, say, it
would if used for pagefile or temp space (which Vista affords with its
ReadyBoost feature which has you using slow flash memory rather than
installing more faster system RAM). SSD drives will deliberately spread out
the files so reduce oxide wear on the memory. It's called wear leveling.
http://en.wikipedia.org/wiki/Wear_levelling
There is a max lifespan (or MTBF) rating for the memory. The more you use
it, the less life is has left. It will wear out. So if you keep rewriting
to the same block of memory over and over, you could end with a catastrophic
fail of the device while other portions of memory have been not used or
little used. Think of like buying a 10-sheet pack of sandpaper. You keep
reusing the same first sheet until it wears out and then throw the entire
pack away because none of it is usable if any sheet is unusable. Instead
you use a little of each sheet until all sheets become used up at about the
same time. Here in another article:
http://www.storagesearch.com/ssdmyths-endurance.html
which was simply found using Google:
http://www.google.com/search?q=+ssd++"wear+leveling"
Below is a canned response that I wrote up before when users were discussing
using flash memory drives or cards to augment system memory.
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 only
endure a maximum number of writes or erases. Flash memory can only be
flashed so many times. Although electronic, they wear out. 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 produce several thousand updates per minute and do
so as long as the app is running. Using Flash memory for Vista's ReadyBoost
as a disk buffer means generating write cycles at a far greater rate and
number than by a user that saves, edits, or deletes music or data files. In
Windows versions without ReadyBoost, some users will use Flash memory for
pagefile space but the number of writes to the pagefile are very high and
will accelerate when the Flash memory fails. 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 but that will tell
you the endurance of the chip, not what masking algorithm is employed by the
flash drive manufacturer that used that flash chip). Typical MTBF for Flash
memory is one million cycles. Sounds high when YOU are the one creating,
editing, or deleting files but that is small change volume for disk buffer
or pagefile usage.
"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 them 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. 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, physical 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. That is why these devices will incorporate fault-tolerant schemes to
mask the failures. More masking (or remapping) as more errors occur results
in more redirects that slow performance, and there is usually a maximum
(spare space used for the masking) after which the device catastrophically
fails.
ReadyBoost or putting the pagefile on Flash memory doesn't speed up Vista by
much and often slows it down. It only helps if the sectors for the data are
scattered to different cylinders on the hard disk for a speed boost of
around 4 to 6%. If the disk has been defragmented or the data is otherwise
serially retrieved from the hard disk, Flash drives actually slow
performance. Flash drives have much slower throughput than hard drives.
Flash memory has a bandwidth of around 3.5MB/s (28Mb/s) for 4KB transfers
and around 2.5MB/s (20Mb/s) for 512KB transfers. An ATA-100 IDE hard drive
can sustain much higher average transfer rates without even considering its
burst mode. Only if the hard disk's heads have to do a lot of bouncing
between cylinders might Flash memory then outperform a hard disk. What most
users report as the noticed speedup by using Flash memory for the pagefile
is a slightly shorter time to load applications, but a faster spinning hard
disk or one that uses perpendicular recording to pack the bits closer
together to effect a higher transfer rate do that, too. You gain little
overall speedup by using Flash for pagefile space but incur a greater
liability to system stability with a device that will slowdown over
continued high usage due to masking and will eventually catastrophically
fail.
ReadyBoost is a problem waiting to happen, and when it happens (not if it
happens) becomes shorter and shorter. The fuse will burn out. Using Flash
memory as pagefile space means eventually you get a hung or crashed OS or
memory corruption errors which means losing data (or worse in saving the
corrupted data). Flash memory is significantly slower than physical system
RAM and can only provide a tiny speedup for highly fragmented files on the
hard disk. Rather than waste money on a Flash thumb drive for ReadyBoost or
for pagefile space, spend it on more system RAM or get a faster hard disk.
You should not incorporate an obviously weak component (e.g., Flash) within
your mass storage subsystem.
Just because Flash memory drives are newer doesn't mean they are ideal
choices to supplant older technology. There are good uses for Flash memory,
as in USB thumb drives or use in digital camera, but don't use it to
supplant real system memory or the highly stressed pagefile on the hard
disk.
OK, thanks for your comments I think you make some good points.
Do you know of a test that actually does what they purport to do that
you would recommend?
The products that I've seen that not only scan but will also make their
suggested fixes (but that doesn't mean you actually want all of them) were
payware. They are diagnostic utilities that have come and go. For some of
PC Pitstop's fixes, they give the manual steps needed to perform the tweak;
however, how many users will actually benchmark the tweak to find out if it
gave them anything truly useful? That's why it is a bit misleading to tell
a user that they need a tweak without giving them proof that it will
actually do the repair or increase the responsiveness or performance of
their host.
How long have you seen registry defragmenters being offered (free or paid)
claiming to speed up your host despite the fact that Windows loads the
registry's .dat files into memory and that's the copy that gets accessed
there after and, as we know, memory is randomly accessed so any part of it
is just as quickly accessed as another part so defragmentation is
irrelevant. Scans that recommend changes should provide some proof that the
change actually helps the user.
