I have ext4 partition, which holds disk image files VirtualBox works with. They all are fixed-size images (i.e. files never change their size). They are defragmented as much as possible (with e4defrag).
I assume that a lot of filesystem features are redundant in this case. I.e. as files are never created, never deleted, never change their size, only reading and "in-place" writing happens, and file contents are aligned on the hard-drive continuously, thus much simpler filesystem could be used in this case (no need for file attributes, directories, journal, etc). Theoretically, I could even use logical volumes instead of files in this case (I am just not sure that I want).
- How to tune ext4 filesystem, to get best performance in this case?
May be another filesystem is more suitable? (Some filesystem that don't support directories, and only continuous fixed-size files?) Or may be Linux has a possibility to mount part of existing partition as a file? I.e. that I create unformatted partition /dev/sda2 and then
- mount K-th to L-th bytes of it as /somepath1/somefile1.vdi,
- mount M-th to N-th bytes of it as /somepath2/file2.vdi,
- and so on.