Some common storage architectures

This section explores some of the more common (and emerging) storage architectures, and maps them to the SNIA Shared Storage Model. You should be able to recognize many familiar products in these mappings, and for the first time, be able to compare a wide range of architectures against a common model.

Direct-attached block storage

Direct-attached block storage is the most common, most mature, least shared, high-performance storage design. It is characterized by:

  • having only one (active) host on each storage interconnect wire,

  • the absence of switches or hubs, and

  • the use of a block interface protocol for operations over the interconnect.


Figure E-17.

graphics/efig17.gif


Aggregation may occur at the device (e.g., array controller) or host (e.g., logical volume manager, software or hardware RAID implementation).

Storage network-attached block storage

Storage network-attached block storage (aka "SAN") is characterized by:

  • multiple hosts and devices attached to a shared storage interconnect,

  • employing a block interface protocol over that interconnect and

  • by configuring each host with a consistent allocation of the shared device resources.

Here, the storage network functions primarily as a communications medium and does not usually provide any block aggregation functionality of its own.

In the case of some storage networks (e.g., Fibre Channel and ESCON-based SANs), the physical distances between hosts and storage devices can be large enough to have two or more sites separated by hundreds of meters, for better failure tolerance. Such schemes fall into this "pure SAN" category only if they do not perform protocol conversions between the sites, or require specialized peer-to-peer connectivity: that is, if the storage network is transparently extended across the site boundaries.


Figure E-18.

graphics/efig18.gif




Designing Storage Area Networks(c) A Practical Reference for Implementing Fibre Channel and IP SANs
Designing Storage Area Networks: A Practical Reference for Implementing Fibre Channel and IP SANs (2nd Edition)
ISBN: 0321136500
EAN: 2147483647
Year: 2003
Pages: 171
Authors: Tom Clark

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