Have they ever solved the problem that after you had written to the same spot on the drive a number of times that spot was now no longer viable?
I remember that being an issue early on; it’s why I don’t own any of these devices.
Nope.
Supposedly NAND flash, the type used for these HD replacements, is not subject to the wearing-out problem.
That same problem would certainly apply to a mechanical device like a hard drive.
I have several 1G and 2G SD chips in various devices, and have never seen any decreases in capacity. And I over-write a lot.
Are you sure you're not thinking of re-writable CDs?
I had a whole flash drive just go totally dead on me a few months back. Nice surprise. Did have a backup, though.
It’s still a problem, but it’s 100,000 write cycles, and various techniques can increase the life of a chip to longer than you’ll probably be using it.
Without going into specifics. My employer did considerable testing before deploying tens of thousands of special purpose machines, using flash memory, which is written over and over again. We've had them in the field for a few years now. I've not heard of any problems.
The durability of one of these flash memory drives is only about 100 years, so, no, the problem hasn’t been solved.
Flash drives use wear-leveling algorithms so that the 100,000 write cycles/page ends up allowing trillions of writes total. Unfortunately, the flash-leveling algorithms are used to emulate a sector-writable device which is then used with a FAT16 or FAT32 file system. If I remember correctly, a 256MB SmartMedia card is divided into blocks of 256 pages of 512 bytes each; each of the page on a block may only be written twice before the entire block is erased. When DOS or Windows wants to write e.g. sector 1234, the flash file system finds a blank page someplace and writes the data there along with a tag saying it's sector 1234; it then marks the old sector 1234 to indicate it's no longer valid. At some point many blocks are going to be full but contain a number of invalidated pages. The wear-leveling algorithm will periodically copy the data from such block into fresh pages. Indeed, to ensure that wear is distributed evenly, even blocks that don't have any invalid data will be periodically moved elsewhere. This ensures that even if a disk is 90% full of files that never change, the "churn" won't always occur in the same 10% that remains.
While wear leveling is certainly a good feature, the approach of emulating a sector-based device and putting a FAT file system on it is a bad one. For good performance, free space should be consolidated, but the sector-based flash systems don't know what sectors the PC file system considers to be "free". Fragmentation can often be a severe problem with older flash drives; had the drives implemented some sort of direct file system, such a problem could have been avoided.