Contiguous Allocation
Allocate files like segmented memory
When creating a file, make the user pre-specify the length and allocate all at once
Inode contents
- location and size
Pros
- simple
- fast
Cons - External Fragmentation
How do you know how large a file will be?
Use Delayed Allocation
- The
writesyscall only affects the buffer cache - Allow write into buffers before deciding where to place it on disk
- Assign disk space only when the buffers are flushed
Other advantages
- Short-lived files never need disk space allocated
- Write clustering
- Find other nearby stuff to write to disk