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SAN-based storage is generally the fastest and the most widely supported. FC and iSCSI SANs communicate using the SCSI protocol, which is a lower layer protocol with very little overhead. SCSI is very mature and widely supported among database, e-mail and other applications. FC SANs sit at the top of the performance pyramid. iSCSI is an emerging, fast-growing interconnect that has several thousand implementations and has entered into the early mainstream of the market. iSCSI is attractive because it doesn't require HBAs or FC switches, which results in lower cost and simplified management.
NAS solutions are traditionally considered to be lower cost and easier to use than SANs. While this is not a hard and fast rule, NAS is more often associated with unstructured data such as documents and images and not for transactional data. NAS is inherently slower than SAN because NAS communicates uses higher layer NFS and CIFS protocols that add latency. The advantage of using NAS is that its file system-level intelligence allows for easier management, protection, migration and control over data. Provisioning and managing storage, as well as sharing files, are much easier than on a SAN.
Object-based Storage (ObS)
ObS is a newer category of storage that has been gaining a great deal of success in the market. ObS (aka CAS) uses a radically different data access approach compared to the traditional address/location method used in other storage systems. ObS creates a unique address of each object and its metadata. The ObS then manages the storage and retrieval of objects and metadata in a very large and flat address space.
ObS systems are being used for archiving reference data such as e-mails, files, applications, images, etc. ObS has gained popularity as part of meeting compliance regulations though its ability to ensure that no one can edit or delete files within a specified retention period. These systems also maintain rich metadata -- or data about data -- that customers can search for quicker access and retrieval as a response to a legal discovery process.
ObS systems add yet another layer of intelligence which impacts performance. ObS is predominantly used as a digital archive and does not require high performance today. ObS is targeted towards massive archives of data and as such should scale to hundreds of millions of objects, which results in hundreds of terabytes of capacity.
Each of these storage personalities has strengths and weaknesses and often their uses can overlap with one another. SAN can be used for file storage and archiving; NAS can be used for database storage; and ObS can be used for some of the same applications as NAS. The convergence of these personalities is taking place with some storage systems supporting both SAN and NAS. This trend should continue and over time customers should see storage systems with multiple personalities that support their applications based on performance, availability and protection levels.
About the author: Tony Asaro is a senior analyst for the Enterprise Storage Group responsible primary storage systems including SAN, NAS and object-based. Tony also manages ESG Lab, a hands-on analysis service of storage technologies and products. Tony brings extensive experience and expertise on storage subsystems, NAS solutions, data management software and SAN infrastructure. Tony has worked for over 18 years as a systems engineer, product manager and other marketing, sales and business roles in the high-tech industry.