Tag Archives: io

Raw vs JFS Logical Volumes I/O

Question

Does Virtual Memory Manager (VMM) work with raw logical updates, and if so, how?
If raw logical volumes do not use block I/O buffer cache, does sync update raw logical volumes or does VMM?

Answer

When an application directly accesses a raw logical volume, the VMM is not involved. The VMM is involved when accessing the Journaled File System (JFS).
sync only updates JFS, so neither sync nor VMM updates raw logical volumes. All writes to raw logical volumes are synchronous, which means that the writes do not return until the data has made it to disk and therefore does not require a sync.