Storage Subsystems - implementation in SAN

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* The storage components of a SAN are the storage arrays. Storage arrays include storage processors (SPs). The SPs are the front end of the storage array. SPs communicate with the disk array (which includes all the disks in the storage array) and provide the RAID/LUN functionality.
* Storage Processors or Controllers:
SPs provide front-side host attachments to the storage devices from the servers, either directly or through a switch. The server HBAs must conform to the protocol supported by the storage processor. In most cases, this is the FC protocol.
* Storage processors provide internal access to the drives, which can be using a switch or bus architecture. In high-end storage systems, drives are normally connected in loops.
* This back-end loop technology employed by the SP provides several benefits:
# High-speed access to the drives
# Ability to add more drives to the loop
# Redundant access to a single drive from multiple loops (when drives are dual-ported and attached to two loops)
* Storage Devices
Data is stored on Hard disk arrays or tape devices (or both).
Disk arrays are groups of multiple disk devices and are the typical SAN disk storage device. They can vary greatly in design, capacity, performance, and other features.
* storage array uses RAID (Redundant Array of Independent Drives) technology to group a set of drives.
* A LUN is a single unit of storage. A LUN is also known as a volume or Virtual Disk or a logical drive, A RAID Group is one or more LUNs with specific RAID level defined.
* Most storage arrays provide additional data protection and replication features such as
snapshots, Clone copies and Remote mirroring.
# A snapshot is a point-in-time copy of a LUN. Snapshots are used as backup sources for the overall backup procedures defined for the storage array.
# Clone copies are actual copy of a LUN, it allows data movement from one LUN to another for an additional copy for testing.
# Remote mirroring provides constant synchronization between LUNs on one storage array and a second, independent (usually remote) storage array for disaster recovery.