In that sense, iSCSI is complementary, not contradictory, to SAS and SATA.Ĭheck out the original article over at TechRepublic.The main difference between SATA and SAS Hard Drives is that SAS drives are faster and more reliable than SATA drives. While SAS and SATA or networking interfaces, iSCSI is a networking protocol that can run across the infrastructure. ISCSI is the storage transport but, at present, there is no such thing as an œiSCSI disk. iSCSI arrays use SAS and SATA disks (which can also be SSDs) for storage, but the data is transported to hosts using iSCSI. However, you might be wondering exactly how does iSCSI compare to SATA and SAS. SSD which deals with how the data is stored.) While this adds resource consumption, the author notes that it also provides a good method to decouple storage from the host, allowing for the share of storage among multiple hosts, as shown below: We can think of iSCSI as a ''storage transportation method.'' In that sense, they resemble SATA and SAS in dealing with how the data is moved around (vs. Data that is transmitted back to the host undergoes this same encapsulation process.īasically, iSCSI adds some extra processor load because of the encapsulation process which takes time.

At the storage array side of the equation, these packets are received and the SCSI commands are extracted from the TCP/IP packet and passed on to the storage device for execution. These TCP/IP packets then traverse the Ethernet network just like any other network traffic. In an iSCSI storage network, SCSI commands originate on the host, at which point, they are encapsulated inside TCP/IP packets. By virtue of the fact that the system is using Ethernet for storage traffic, speeds of both 1 Gbps and 10 Gbps are supported. It™s either hardware- or software-based and controls communications with the Ethernet-based storage array. The above image includes an iSCSI initiator in the host server: It simply utilizes a different method of storing the data.

In other words, the SSD functions no differently than a hard-disk in terms of how it the interfaces (SAS or SATA) work. The initiator, functioning as the system controller, communicates with the SSD using the appropriate commands as dictated by the host interface (again, SAS or SATA.) SATA disks can be connected to SAS expanders and initiators, but do not perform quite as well as SAS disks.Įach drive has its own host interface (SAS or SATA) which are connected to an initiator or an expander. A target is either a SAS drive or a SATA disk. Expanders are sort of like network switches in that they can direct traffic and they provide the ability to scale the SAS architecture beyond single port limits. Expanders sit between initiators and targets, but can also connect to other expanders, as you can see in Figure A. The initiator is the SAS controller to which SAS expanders or targets can be connected. Think of SAS and SATA as different kinds of computer interfaces, such as PCI Express, but there are actually multiple components that make up the overall SAS architecture. SATA and SAS are storage interface and bus types designed to aid in the movement of data from one place to another. For anyone who has ever had a difficult time understanding and differentiating these technologies, this is a very valuable resource. Yesterday there was a great piece over at TechRepublicon the confusing intersection of SAS, SATA and iSCSI arrays.

Sas vs sata