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Re: SVNCopy - The coolest tool for moving and syncing WCs!

From: Thomas Hruska <thruska_at_cubiclesoft.com>
Date: 2006-07-21 18:58:15 CEST

si wrote:
>> Yves Reynhout wrote:
>> > Why not just put the WC on a stick and be done with.
> Exactly.
>> Because you can only write a few thousand times to a USB memory stick (I
>> assume this is what you are referring to) before the flash RAM fails.
>> More can go wrong, IMO, by doing that.
> If you had said a few hundred thousand then it might have been believable,
> but only a few thousand? nonsense...
> http://en.wikipedia.org/wiki/USB_flash_drive
> "Like all flash memory devices, flash drives can sustain only a
> limited number of write and erase cycles before failure. Mid-range
> flash drives under normal conditions will support several million
> cycles, although write operations will gradually slow as the device
> ages."

Thanks for the link. However, nothing in the article says what
constitutes an "erase/write cycle". Most OSes actually intervene for
USB mass storage devices and don't actually write any data to the drive
until sufficient data has been acquired in RAM for a write operation so
as to lengthen their lifetime and to shorten write operation times from
applications. So, if the power goes out or you pull the USB drive
instead of properly ejecting, poof! There goes your changes (best case)
and possibly your project (worst case) and you get the bonus of file
system corruption (have had both happen with non-important data - I
learned to eject the device after the first time).

Flash RAM has historically only been capable of a few thousand write
operations before failure (writing, from my perspective, means filling
and emptying every bit available). I know that early USB flash drives
had the same problem with limitations of up to 10,000 writes. If it is
up to 500,000 writes then clearly something has changed. The truth is:
  No one has really bothered to test the true lifespan of flash RAM in
USB thumbdrives to get a real number.

Flash drives are "cool" but I don't trust them for anything but moving
common data let alone critical data.

Thomas Hruska
CubicleSoft President
Ph: 517-803-4197
Safe C++ Design Principles (First Edition)
Learn how to write memory leak-free, secure,
portable, and user-friendly software.
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Received on Fri Jul 21 18:58:33 2006

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