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 storageDirect-attached block storage is the most common, most mature, least shared, high-performance storage design. It is characterized by:
Figure E-17.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 storageStorage network-attached block storage (aka "SAN") is characterized by:
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. |