We've been hearing for a long time about running storage over IP, particularly using the iSCSI protocol. We take a look at the technology, its applications, and some of the devices you can use.For a long time now expanding storage meant buying more servers and disks. This has proved to be a costly method for increasing storage, and is often an inefficient way of doing things.
We are now instead using storage area networks (SAN). This term generally relates to a bank of storage devices for multiple servers and/or networks that may be accessed in a local area network (LAN) or wide are network (WAN).
The key benefits here are: increased disk utilisation, improved data availability, improved performance and protection of data. SANs also reduce the loads that are placed on servers.
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.
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