Datacenter storage technology has three main flavors:

• Direct Attached Storage (DAS): This is the traditional storage solution, where disks are attached directly to servers. Access is generally arbitrated by an intelligent controller.
• Network Attached Storage (NAS): Here storage is essentially at a filesystem level and is shared between multiple servers using some sort of networking protocol. The remote filesystem is "mounted" at a specific location in the server operating system's filesystem tree. Two common NAS protocols are NFS (Network File System) and CIFS (Common Internet File System). CIFS requires a dedicated separate storage server which all of the other servers to connect in order to access the data. Besides allowing for the sharing of data, the key advantages of NAS are as follows:
  • More efficient utilization of available storage capacity
  • Centralized management
• Storage Area Networks (SAN): Just like NAS, an SAN offers shared storage. However, SANs provide block-level access instead of sharing filesystems. This means file sharing is not possible, but the other advantage of efficient utilization is retained. SANs sometimes use specialized networking (such as Fibre Channel) in addition to the storage servers. The iSCSI protocol is a SAN solution that uses existing Ethernet devices and IP protocols, hence enabling a cost-effective SAN solution.