memtech flashdrives

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We are using 4GB IDE memtech flashdrives in one of our embedded
devices. We have had about 10% defective among those used
under normal conditions by our customer.
During the qualification, particularly for the vibrations
we have had 50% defective hard drives.
The drives are ruggedized, -40 +85 deg celsius.

Have you experienced similar problems?

We have asked memtech for an expertise but so far, without
any reply from them.

The problems are undetected drives, or corrupted boot sector
or corrupted clusters.

Regards


Re: memtech flashdrives

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How often do you write to the drive?  We only write during boot and
shutdown on our flash drives.  We never have much problem as you
described.  Do your customers happen to turn off power while writing to
the drives?

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Re: memtech flashdrives


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I must confess we use the Windoze 2K OS and so the drive is used
by both the OS for swapping and by the application.

We do not know how much write the customer application perform
per second.

The problems we have met, particularly for the vibration tests
during the qualification were found with new drives and a low
amount of disk writes.

I don't think the problem comes from overwriting the same memory
location too many times, thus exceeding the limited number
of cycles for the flash, since the problems often appear
at the beginning of the tests when only few write access
have been made.

We also suspect problems perhaps with power supply spikes
or ribbon cable twists that could occur due to vibrations.

I have read somewhere that flashdrives were considered not
very reliable and that a defect rate of 10% was announced.
I don't remember where this was written and for what
operational conditions that was claimed.


Re: memtech flashdrives


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This will definitely kill the flash drive, it's just a matter of weeks
(perhaps months).

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It doesn't matter.  The OS is bad enough for the drive.

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They must have poor solder joints.  Actually, very poor joints that can
be loosen with vibration.  Most electronics (include Compact Flash, as
we use in ours) can sustain 10G or greater shocks.

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Try placing some large caps on the power line near the drive.

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They are very reliable if you use them properly.  Namely, run in
read-only mode and write for occasional updates.   Flash manufacturers
do not recommend using them as read/write drives.  Unfortunately,
resellers (memtech?) don't follow the guide lines in pushing sales.

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Re: memtech flashdrives


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You are certainly right about the OS, but unfortunately, this is
a request from our customer. We could perhaps try using a ramdisk
for the swap but we have just replaced magnetic drives with these
ones and of course, there was no problem with those, except during
vibrations, that's why.
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Agreed. We are now looking at Windoze XP embedded which includes
a filter that prevent write access to the drives. That will perhaps
solve our problems, provided the customer will accept to upgrade
its application.
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most interesting


We will try that, thanks

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We should be able to do this thanks to the file filter
in XP embedded

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Re: memtech flashdrives
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Have you looked at the Hitachi EnduraStar range? These are 20 or 30GB
ruggedised 2 1/2" drives, designed for automotive applications.

Rob



Re: memtech flashdrives


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Operating Vibration (sine wave)      1.0 G (22-500Hz)
Non-operating Vibration (sine wave)     5.0G (22-500Hz)

If you hit a pot hole, there can easily be more than 1G force.
Fortunately, no auto maker would use hard disk for mission critical
part.  Or, do they?

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Re: memtech flashdrives


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A kick in the device by a footballer (soccer) is much more than 40G

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They sometimes connect radiosets on the same fieldbus as safety
devices, such as speed regulators, about which we have heard some
interesting stories, here, recently;)


Re: memtech flashdrives
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A pot hole would cause a vibration for temporary loss of data.
CF:15G, HD:1G

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A ball hit would cause a shock for permanent damage.
CF:1,000G HD:250G

For more comparative data between Compact Flash Drive and Hard Drive:

http://cfd.linnix.com/spec.html

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