Systems Management Planning, Inc.

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Storage Services

Strategy, Selection, Design and Installation
SAN and NAS Technology
Storage Resource Management
Software and Hardware Solutions

NAS vs. SAN Comparison

Network Attached Storage (NAS) technology and Storage Area Network (SAN) technology are different but complimentary.

NAS

When someone uses NAS, the NAS server(s) SHARES DIRECTORIES and FILES via the ETHERNET NETWORK to various client systems. The client systems many times are users' PCs and sometimes other application servers. Commonly used protocols are Microsoft CIFS and UNIX NFS. Characteristics of NAS are: It is a FILE SHARING technology; requires bandwidth on the company's ETHERNET network; is not typically used for I/O intensive applications such as database and ERP packages due to the inherent limitations of a non-Gigabit Ethernet; is the lowest cost storage to implement and manage.

SAN

When someone uses a SAN, they are implementing a multi-Gigabit fiber network, using Fibre Channel protocol, that is USED EXCLUSIVELY FOR APPLICATION SERVER TO STORAGE I/O. This network is completely separate from the company's Ethernet and is generally much higher performance. SANs allow for HIGH PERFORMANCE DISK BLOCK SERVING to various application and files servers. Characteristics of SANs are: DISK BLOCK SERVING TO SPECIFIC SERVERS or CLUSTERED SERVERS; allow for optional NO SINGLE POINT OF FAILURE configurations; VERY HIGH I/O PERFORMANCE; allow for consolidation of storage and storage management; provide for backups via the SAN (not putting traffic on the company Ethernet) when using a SAN-attached tape library; more costly to implement than NAS but still provides lower cost of ownership and management than direct attached storage.

NAS and SAN are two completely different technologies which serve different functions. They are complementary because NAS servers can obtain massive amounts of high performance storage by being attached to a SAN, rather than using a finite amount of server-specific direct-attached storage. Both technologies allow for better, lower cost-of-ownership for storage as compared to individual server direct-attached storage, especially as a customer’s environment grows. Typically, a human being can effectively manage about 10X the amount of storage in a SAN as compared to direct-attached storage.

SANs also can be configured to provide SNAPSHOTS (point in time copies) of data and be configured to synchronously or asynchronously mirror data to another location such as a disaster recovery site.

Another “version” of a SAN uses iSCSI protocol over Ethernet medium rather than the Fibre Channel protocol over a private fiber medium used by traditional SANs. The result when using iSCSI is the same as when using FC, LOGICAL BLOCK STORAGE PRESENTED to a client server. The advantage of using iSCSI is the lack of the costs associated with a Fibre Channel infrastructure. The disadvantage is that the performance is inherently much lower and doesn't scale. This is due to the nature of CSMA/CD Ethernet technology and will be mitigated to some extent when 10Gig Ethernet is available.