to use for allocation size and alignment. For RAID5/6
systems this should be the number of data
disks * RAID chunk size in file system blocks.
-delalloc (*) Deferring block allocation until write-out time.
-nodelalloc Disable delayed allocation. Blocks are allocation
- when data is copied from user to page cache.
+
+delalloc (*) Defer block allocation until just before ext4
+ writes out the block(s) in question. This
+ allows ext4 to better allocation decisions
+ more efficiently.
+nodelalloc Disable delayed allocation. Blocks are allocated
+ when the data is copied from userspace to the
+ page cache, either via the write(2) system call
+ or when an mmap'ed page which was previously
+ unallocated is written for the first time.
max_batch_time=usec Maximum amount of time ext4 should wait for
additional filesystem operations to be batch