Storage over IP: what is it good for?

Fibre channel (FC) has been the main way of interconnecting servers and storage devices in SANs for some time now. However, it's very expensive. IP storage, or in particular iSCSI, is a fairly new technology offering lower costs and easier deployment than fibre as iSCSI uses standard Ethernet technology to create storage area networks and greater connectivity.

If you want to get more technical, iSCSI or Internet SCSI is an IETF standard that maps SCSI blocks into Ethernet packets. The iSCSI protocol is a method for transporting low latency SCSI blocks across IP networks.

There are a few other terms we should clear up before we go on. You may have come across the terms Direct Attached Storage (DAS) and Network Attached Storage (NAS).

The differences here are quite simple. DAS units allow system administrators to connect them directly to a server typically via SCSI -- some DAS arrays actually allow multiple servers to be connected directly to them and share their resources, and also provide server redundancy too if required.

NAS are specialised file servers for Ethernet-based networks. NAS boxes allow administrators to connect them somewhere on the local area or wide area network for remote access. By simply attaching a DAS or NAS device directly to a server or on your network you can instantly increase your storage capacity by 1TB or more.