Re: [reiserfs-list] 'let the hdd remap the bad blocks'
Hans Reiser [EMAIL PROTECTED] writes: Just taking a guess, many hard drives have difficult and time-consuming procedures that they can go through to read a troublesome block. These can take 20-30 seconds. Probably if they have to go through these procedures, once they finally succeed the smart vendors remap the block. They should try to rewrite and write verify the block before remapping it, as there is only a finite amount of spares. For SCSI drives, there's also Jörg Schilling's sformat tool that can do the badblocks stuff directly in the drive rather than through all the kernel buffers, and can also refresh or reassign bad blocks. -- Matthias Andree
Re: [reiserfs-list] 'let the hdd remap the bad blocks'
Matthias Andree wrote: Hans Reiser [EMAIL PROTECTED] writes: Just taking a guess, many hard drives have difficult and time-consuming procedures that they can go through to read a troublesome block. These can take 20-30 seconds. Probably if they have to go through these procedures, once they finally succeed the smart vendors remap the block. They should try to rewrite and write verify the block before remapping it, as there is only a finite amount of spares. For SCSI drives, there's also Jörg Schilling's sformat tool that can do the badblocks stuff directly in the drive rather than through all the kernel buffers, and can also refresh or reassign bad blocks. Vitaly, take a look at that. Part of a good user interface is letting users know what tools are available. Remember, most users will encounter a failing drive and/or fsck on a journaling fs as a rare and stressful event in their lives, so it is good to educate them with URLs and other references at the time they run fsck.
Re: [reiserfs-list] 'let the hdd remap the bad blocks'
On Tue, 20 Aug 2002, Hans Reiser wrote: Vitaly, take a look at that. Part of a good user interface is letting users know what tools are available. Remember, most users will encounter a failing drive and/or fsck on a journaling fs as a rare and stressful event in their lives, so it is good to educate them with URLs and other references at the time they run fsck. A propos URL, here we go: ftp://ftp.fokus.gmd.de/pub/unix/sformat/ -- Matthias Andree
Re: [reiserfs-list] 'let the hdd remap the bad blocks'
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
Re: [reiserfs-list] 'let the hdd remap the bad blocks'
Oleg Drokin wrote: Hello! 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. Bye, Oleg On Mon, Aug 19, 2002 at 03:58:30PM +0100, Newsmail wrote: Hello Hans and Oleg, maybe its an offtopic question, but Hans always talks about leaving the hard disk to remap the bad blocks by itself. could you explain it in some words, how all this works, what happens after, and since when it exists, or do you have any special URL explaining this? thx in advance, greg Just taking a guess, many hard drives have difficult and time-consuming procedures that they can go through to read a troublesome block. These can take 20-30 seconds. Probably if they have to go through these procedures, once they finally succeed the smart vendors remap the block. Hans
