Re:Five-Disk Floppy Raid: 4MB of Blistering Fast Storage (2009)
by M95D on Thursday December 07, 2023 @09:02AM
(#38556406)
btrfs doesn't support bad blocks. It's written in the documentation.
From experience I can tell you that most usb sticks fail while reading back data by returning bad data, not an error or timeout, and the defective sectors aren't always the same (internal remap to wear leveling might be the cause of that).
Advice: Do md-raid0 on half of them, md-raid0 on the other half, and btrfs raid1 on the two md devices. If you want to exceed 25MB/s, use different USB controllers, not different ports on the same hub.
Re:Five-Disk Floppy Raid: 4MB of Blistering Fast Storage (2009)
by o11c on Thursday December 07, 2023 @11:57AM
(#38558742)
Btrfs doesn't directly support bad blocks. But since the conversion is supposed to use only "free space" that's presumably excluding bad blocks (which are presumably counted as allocated).
Re:Five-Disk Floppy Raid: 4MB of Blistering Fast Storage (2009)
by M95D on Thursday December 14, 2023 @07:11AM
(#38640517)
Doesn't support bad blocks at all.
Bad blocks don't count as allocated unless they are newly discovered - data should be moved asap if it's still recoverable. An allocated block with nothing in it is an error.
From the fsck man pages, only ext2, ext3, ext4, and reiserfs support it. I hope that `btrfs-convert` deals with it correctly, but you must not ever run `btrfs balance` or delete the backup (it won't waste space if it was a fresh FS). And if further bad blocks develop you'll have to redo this all from scratch.