Oleg Drokin <[EMAIL PROTECTED]> writes: > Basically uyou'd better search for this on HDD vendors sites. > What's going on is simply can be described this way: > You write some block to HDD, if HDD decides the block is bad for some reason > and remapping is allowed (usually by tiurning on SMART), block is written to > different on-platter location and drive adds one more entry to its > remaped-blocks list. Next time you read this block, drive consults its > remapped blocks list and if block is remapped, reads it from new location > with correct content. > Described mechanism works for writing. > Actually I've seen something that looks like remapping on read, though > I have no meaningful explanation for that (except that they may have some > extra redundant info stored when you write data to disk, so that if sector > cannot be read, its content is restored with that redundant information and > sector is then remapped.). And this process takes a lot of time.
My Fujitsu MAH-3182MP drive (SCSI actually) had ARRE enabled as it shipped, but ARWE disabled, for reasons I cannot tell, not even from the data book (PDF). That's Automatic Remap on Read/Write Error. I'm not sure what it really means, but if the drive really remaps on a read error, it's going to leak a block at power loss while it is amidst a block write the next time this block is read. So I switched that to do ARWE. IDE users are not too lucky unless their vendor provides them with a tool (and not many ship raw floppy images, many have some multi-MB Windoze tools just to write some hundred kByte to a floppy disk...) -- Matthias Andree
