User:Rajdivecha/Storage systems

Storage systems are specialized systems that efficiently stores data. Storage systems are different from storage devices like Hard disks, CD-ROMs, RAM/ROM etc. rather they encapsulate storage devices namely hard disks.

In layman's term a storage system is a huge disk (virtual/imaginary) where the user's data can be stored.

Many companies or research organizations have vast amount of data like images, documents, videos, emails etc. to be stored. Not just the storing of data is important but at the same time recovery of critical data is also important. For example, research documents, if lost by accidental deletion or electrical malfunctioning could cause huge intellectual as well as monetary losses.

The amount of data to be stored is so huge that even the hard disks available, with the maximum capacity in the market is not sufficient. Secondly, it is technically impossible (or not feasible) to create huge hard disks that can hold vast amount of data. This is where a storage system comes handy.

Construction
A storage system consist of one or more boxes known as Enclosure which holds N number of interconnected hard disks. This enclosure is then connected to the HBA (Host Bus Adapter) which is fitted into a vacant peripheral connector slot in the computer (know as the Host).

Advantages of interconnected disks
 * 1) You have a huge capacity disk formed by a collection of more than one disks.
 * 2) The capacity can be increased in future by adding more disks.
 * 3) Besides storage, techniques for duplicating the data can also be employed.
 * 4) Disks can be dynamically removed or added i.e., your computer keeps running while this is done.

The storage system has a specialized software (or firmware) running on it that makes the host believe it is connected to a disk (can be one or more than one) rather than something else. Besides the disks, the enclosure might house other devices like fans, temperature sensors, power supplies, alarms etc. These devices help in keeping the disks error free as far as possible by giving early warnings of any predicted failures. They are continually monitored and controlled by the software/firmware running on the enclosure.

These disks or more specifically volumes or logical units (LUs) are created with the help of a configuration utility for that system. The most common protocol used to communicate with the LUs is SCSI. A LU can reside on either a single disk or span across multiple disks in the enclosure based on the size and the RAID type parameter set by the user.

Storage systems are available in many shapes and sizes. Some are as small as 5 hard disks stacked one on top of the other and some are as huge as a single, double or multi-door wardrobe.

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Connectivity
There are many options available for connecting the storage system to the host.


 * DAS: Direct Attached Storage
 * SAN: Storage Area Network
 * NAS: Network Attached Storage

Features
The features vary from vendor to vendor. Some of the key features associated with the storage systems are as given below.


 * High performance
 * High availability
 * Data integrity
 * Hot swapping
 * Support for SAS, SATA or both drives
 * Support for Fibre Channel or iSCSI
 * Redundant storage processors
 * Replication (local / remote)
 * Mirrored memory
 * Batter backup
 * High bandwidth (4 Gb/s etc.)
 * Scalability
 * Non-disruptive data mobility
 * Management software
 * Interoperability
 * Fault tolerance
 * Clustering

Vendors
Below is small list of vendors. Search for others by googling them with the keyword 'Storage systems'.


 * Adaptec, Inc.
 * NetApp
 * EMC Corporation
 * HP
 * Helio Solutions, Inc
 * Hitachi
 * IBM
 * Intransa, Inc.
 * LeftHand Networks
 * Open Source Storage
 * and many more...