"It's hard to get consistent performance" out of hard disks, Vogels said. Due to the time it takes for the hard drive's mechanical head to jump from one location of the platter to the next, occasionally a read or write operation will take far longer than the average performance of that disk, he said.
In contrast, flash drives "are really good at providing consistent rapid I/O," Vogels said. For SSDs, any cell of data is equally as accessible as any other cell. "If you are really interested in building system performance, then you need SSDs as the core of your system to manage I/O."
To back up his point, Vogels referenced a presentation from engineers at Instagram that found that moving to SSDs allowed the service to deliver data to its service 20 times as quickly.
AWS has not announced when I2 instances will be ready for consumption, though it did provide more information about their configuration.
I2 will come in five different instances that span from one to eight 720GB SSDs. The largest I2 instance, called i2.8xlarge, will deliver 350,000 random read IOPS and 320,000 random write IOPS.