Just curious... I've been wondering if it would possible/useful to make a btrfs mode where it _always_ writes in a ring on the entire disk. Since it can write "anywhere" already, it could just write sequentially always. The write process would have to be changed to read a blob, throw away the garbage, and fit in the new stuff in the gaps, then write the blob. Write performance would degrade to half once the disk is half full of stuff that can't be thrown away, but then almost all file I/O patterns should be about the same speed, because disk writes are only sequential. Or is it that it's pretty much always like this until space is tight anyway? I suspect that eventually free space will be pretty fragmented, and it'll have to seek a lot just to write in available space. Perhaps the performance is similar or worse to sequential read+write versus just writing in the gaps in many/all cases? Maybe this what nilfs2, etc., are all about, in which case maybe it would be neat to have a mount option or even realtime heuristic-based switching if load patterns fit better to a particular mode... Simon- -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
