4K, why not also 64K?
4K, why not also 64K?
Posted Mar 12, 2009 19:11 UTC (Thu) by zmi (guest, #4829)In reply to: 4K, why not also 64K? by james
Parent article: Linux and 4K disk sectors
> I've actually done the math. Even 64kB pages is totally useless for
> a lot of file system access stuff: you need to do memory management
> granularity on a smaller basic size, because otherwise you just
> waste all your memory on unused left-over-space.
> a lot of file system access stuff: you need to do memory management
> granularity on a smaller basic size, because otherwise you just
> waste all your memory on unused left-over-space.
Depends on the design of the FS. Example: ReiserFS already combined the endings of several files in a single 4K disk block and thus saved a *lot* of disk space. And for a company using the server to store their documents, there won't be too many files anymore with <64KiB (yes I know with 65KiB you still loose 63KiB), but those should be fast. Speed starts to be a limitation, while disk space is not (hey, just put another terabyte disk into the RAID).
Regarding memory page size: I don't understand why that limits a FS block size, there's scatter/gather I/O and a 64KiB block from disk doesn't need to be linear in memory. I'm not a coder, but I think that limitation should be resolvable.
zmi