On 10/19/2015 11:05 PM, Linda Walsh wrote:
Don't know where you get your information, but you might want to re-examine some of the sources, as they are provably inaccurate.
What I wonder about ... True b-tree systems such as ReiserFS follow a b-tree allocation *AND REALLOCATION* policy. Yes file systems that use a model where the directories are just a specially marked file (harks back to the old V6/V7 FS! WOW KISS) are by their very nature going to have problems such as gaps for deleted files and quite probably linear searches. Perhaps that's why Postfix and others use a slightly hierarchical "indexing" scheme. Many email systems are high throughput and this seems to be one tactic Postfix uses. If the directories are part of a b-tree then a whole host of problems about allocation and searching go away. Hmm. Other problems arise, but that's another matter. <quote src='http://cs.uns.edu.ar/~jechaiz/sosd/clases/slides/07-FileSystemsExtra4_Reiser.pdf"> "The simplest method of implementing a directory is to use a linear list of file names with pointers to the data blocks ... The real disadvantage of a linear list of directory entries is the linear search to find a file. ... Directory information is used frequently, and a slow implementation of access to it would be noticed by users. </quote> There's more, but its worth reading the slide deck. I don't know about the other B-tree file systems. Ext3 did store directories in a linear table but there was also the 'dir_index' option. I presume this is available for ext4 as well. O don't know if its purely indexing or how it affects creation/deletion if the directory structure underneath is still linear. I do now that there are problems with dynamic rebalancing of b-trees when they exist on dis; in short there can be delays when they get re-written due to balancing. ReiserFS apparently solved some of these, but I see the occasional delay on my BtrFS ones. I don't use XFS so can't comment. -- A: Yes. > Q: Are you sure? >> A: Because it reverses the logical flow of conversation. >>> Q: Why is top posting frowned upon? -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org