8/7/2023 0 Comments Macos livejournal![]() For HFS+ filesystems, the catalogue B-tree is the "master index" where all of the directory/filesystem structure is stored. This Mac had lost power during bootup, and had its catalogue B-tree damaged. For a proper block remapping with the usual means, a data backup is needed, then a destructive surface test, writing to bad blocks. Reliance on the bad block remapping is somewhat dumb, too, as a bad block is treated as bad (by the drive) only when it can't be written to, not when reading fails. Snag is, bad blocks appear sooner than they're remapped if the OS ignores them at filesystem level. This is a finite resource, so once a drive runs out of remappable blocks, a filesystem on it can crumble. Modern ATA hard drives come with a cluster of spare blocks that can be used to replace damaged blocks. And it will read/write to a delicate damaged area as if nothing's the matter (eventually causing more bad blocks to appear, and causing the entire filesystem to crumble). OS X has rudimentary support for bad block marking (they can be manually reassigned to a Unix "bad block" file), but it tries to rely on ATA drive bad block remapping. When Windows or Linux encounters a bad block during a file operation, it marks it as bad the filesystem will omit it. MacOS 9 (and pretty much any OS) had a surface scan option for its disk utility, which could be used to locate bad blocks. A Mac had shown up recently with a damaged hard drive it can be quite an ordeal when it comes to data recovery off a Mac, so well, here's a summary of all the trouble.įirst of all, MacOS X lacks some basic functionality when it comes to bad blocks on hard drives. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |