The general consensus on mixed workloads includes 80% reads in client environments and 70% reads for workstations.
SATA-based devices are half-duplex; they can only read or write at a time, not both. Products based on the SCSI command set (including SAS) are full-duplex; they can read and write simultaneously. Full-duplex devices fare much better in mixed-workload environments.
Boot drives are subjected to mixed workloads since the system is constantly reading and writing small pieces of data. When you start an application, the software opens as a series of reads, but also logs (writes) data to the host. And this happens hundreds of times per minute.
Secondary drives used for bulk storage change the read write ratio. They do not log operations, but read and write when transferring files to and from the system. Most secondary drives hold data that is transferred sequentially. Movies, music, picture collections and other media files make up the bulk of secondary storage.
In the next section, we'll look at different transfer ratios and how sequential data reacts while multitasking in a secondary environment.