NAS vs. SAN 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 1

Introduction Network Attached Storage (NAS) and Storage Area Networks (SAN) are storage architectures that have gained momentum in the last three to five years that aim to provide businesses with cheaper, more scalable, and manageable alternatives for their ever-growing data requirements. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 2

Server-attached storage (traditional way) on network servers running general-purpose operating systems, such as Unix,Windows provide access to file systems that can be shared among users while also delivering a variety of other functions, such as distributed printing, directory services, mail delivery, Web hosting, database transaction, and many other network services. The classic network server uses some form of SCSI host adapter or RAID controller that in turn connects to groups of disk drives. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 3

The primary advantages of server-attached storage involve simplicity of implementation and modest cost. The disadvantage of this model is scalability. As storage capacity requirements increase to the multiterabyte level, and as data sets need to be distributed among multiple applications or servers, economy and simplicity both fall away. The shortcomings of the basic server-attached storage model led to the rise of the NAS and SAN alternatives. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 4

Comparison NAS model can be considered a mature technology, with commodity products available for small workgroups to enterprise wide data centers. SAN represent a still-evolving technology that targets organizations with large-scale and complex data storage requirements. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 5

NAS Almost any machine that can connect to the LAN (or is interconnected to the LAN through a WAN) can use NFS, CIFS or HTTP protocol to connect to a NAS and share files. SAN Only server class devices with SCSI Fiber Channel can connect to the SAN. The Fiber Channel of the SAN has a limit of around 10km at best 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 6

Typical NAS 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 7

Typical Fiber Channel SAN 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 8

A NAS identifies data by file name and byte offsets, transfers file data or file meta-data (file's owner, permissions, creation data, etc.), and handles security, user authentication, file locking. A SAN addresses data by disk block number and transfers raw disk blocks. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 9

In NAS Backups and mirrors (utilizing features like NetApp's Snapshots) are done on files, not blocks, for a savings in bandwidth and time. A Snapshot can be tiny compared to its source volume. In SAN Backups and mirrors require a block by block copy, even if blocks are empty. A mirror machine must be equal to or greater in capacity compared to the source volume. In NAS, File System managed by NAS head unit. In SAN, File System managed by servers. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 10

NAS unit can become a serious bottleneck in high transaction environments. since a SAN doesn't have to use IP to transfer data to the servers, the conversion of data blocks into IP packets (which is done in NAS) doesn't have to take place, and this reduces latency. NAS communicates via NFS(for unix) and CIFS(for win) protocol to transfer data. SAN communicates via FCP protocol to transfer data. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 11

NAS provide a degree of data protection by producing internal backups. These backup images use hashing or compression technologies to minimize the amount of space. In a volatile data environment, data snapshots can be taken every hour. This type of process does offer the ability to easily recover files lost through accidental deletion or software malfunction but not system failure. SAN involves reliability and fault tolerance. It includes many redundant components. Its internal disk systems will rely on RAID configurations that continue to operate even when one or more disk drives fail. Multiple controllers and power supplies provide protection. The use of multiple fibre channel switches creates a fabric of connectivity. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 12

The leading suppliers of NAS storage are Network Appliance and EMC Corporation. A number of other vendors including Auspex Systems Inc.; Compaq Computer Corporation; Dell; Hewlett-Packard; IBM; Maxtor Corporation; Network Storage Solutions; Procom Technology, Inc.; and Snap Appliances. The leading suppliers of SAN are EMC Corporation, Hitachi Data Systems, IBM, Sun Microsystems, Hewlett Packard, Dell Computer Corporation, and Compaq Computer Corporation. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 13

Technology Alternatives Storage over IP (SoIP), also known as iSCSI (Internet SCSI), is a technology that has emerged in the last year that relies on Ethernet and IP network protocols to create a storage network rather than Fiber Channel technologies on which current SANs are based. 10/2010 Palestinian Land Authority IT Department By Nahreen Ameen 14