When it comes to I/O constraints, numerous things can be done on your system without the need for more hardware. You may need to do some database tuning to reduce the I/O performed by your SQL or query based application. You might need to optimize the use of operating system journaling to improve I/O performance.

Your batch processing could be generating thousands of pages of spooled files that are not being accessed by any end users. You may have transaction history database files on your system that have not been purged or archived in 12 years. Numerous batch analytical reporting jobs may be running during peak business hours rather than being scheduled for off hour processing.