We all are aware of Buffer Pool and its importance while querying database.
When ever there is request for data , data and index pages are read from disk into the buffer pool
Also from buffer pool modified pages are written to disk during checkpoints. These pages are then read again from disk.All this random I/O activities putting pressure on disk.In general to resolve this issues we have to add RAM or high performance disks. All this leads to cost escalation and more Disk and Ram cause hardware failure.