Wednesday, July 29, 2009

Common fables of clustered storage.

Clustered storage is a networked collection of nodes and irrespective of the number of nodes in the cluster there is only one logical management view. This significantly simplifies the management task and this combined with other interesting attributes of clustered technology has helped to broaden the appeal of this storage technology.

Clustered storage is a solution which historically has been restricted to the HPC world (high performance computing) but its evolution has made this architecture relevant for commercial application and more specifically for the small and medium sized enterprise.

However the attitude towards clustering is clouded by a number of well documented {(StorageIO) (The Guru) (humsurfer)} fables circulating about this technology. The following is my take.

Fable 1: Clustered storage is only for high performance environments.
Fact: It is true that clustered storage had its beginnings in the HPC arena but now clustered architectures are equally effective for general purpose SAN or NAS applications or bulk storage and archiving applications.

Fable 2 : Clustered storage is only for large data centers.
Fact: Clustered architectures have many interesting attributes that meet the requirements of small and medium sized enterprises. It is no longer an option restricted to large enterprises.

Fable 3: Clusters and Grids are different storage architectures.
Fact: Essentially a grid and a cluster is the same thing the only difference is in the mind of the marketer.

Fable 4: Clustered storage is only appropriate for parallel or sequential access.
Fact: Bandwidth hungry applications are not the only use of clustered storage. I/O intensive applications such as OLTP or perhaps file serving, archiving or bulk storage applications are equally applicable. It is a storage architecture that has broad commercial application.

Fable 5: Only NAS storage can be clustered.
Fact: Not so block based clustered solutions are available that support FC and iSCSI with a number offering a unified configuration that supports both block and file protocols on the same appliance.

Fable 6: Clustering improves performance.
Fact: While it is true that clustering can improve performance it also improves scalability, flexibility and capacity

Fable 7: A clustered pair is a form of clustered architecture.
Fact: Not so. The term clustered pair has been used to describe two controllers that simply have fail over capability. This is not a clustered architecture.

Clustered storage is gaining appeal in a broad cross-section of commercial environments with
much enlightened material being published; worth reading is the latest blog at StorageI/O.

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