The typical hard drive form factor – either 3.5” or 2.5” in physical size – is one the most popular form factors in which to deploy flash storage as well. This is no surprise given that flash disks are often used on server hardware as storage vendors have embraced the use of commodity hardware as their platforms of choice. These devices, like hard drives, sport either SAS or SATA connectors in order to connect to their host servers. As such, the system sees each of these flash disks as just another place to store data.
The disk=based form factor is the most versatile one available today. Every server has SAS/SATA ports and, therefore, can accommodate a solid state disk. SSDs have revolutionized the storage industry and are the most popular flash types available today.
SAS/SATA-based SSDs are generally far less expensive than PCI-e-based storage cards. They carry a lower cost per gigabyte than PCI-e cards, but they also support fewer IOPS.
Compared to their PCI-e brethren, however, SAS/SATA-based SSDs have a storage controller with which to content, which introduces abstraction – and thus, latency – into the storage equation. Of course, not all SAS/SATA controllers are created equal, so some controllers will be better and others will be worse. Of course, regardless, SSDs remain much faster than rotational disks. SAS/SATA-based SSDs are generally far more expensive than PCI-e-based storage cards. They carry a lower cost per gigabyte than PCI-e cards, but they also support fewer IOPS.