| Management of business data is becoming ever more | | | | disks, and rebuilding the storage array. In small |
| complex and important with increasing pressures of | | | | institutions this setup can work well, but it gets very |
| security, regulatory compliance, and corporate | | | | difficult to manage as the number of servers |
| governance. Technology is allowing businesses to | | | | increases. Backups become more challenging, and |
| create and store exponentially more data. | | | | because storage is not shares anywhere, storage |
| Understanding how to make the most of your data | | | | utilization is typically very low in some servers and |
| storage andcentralizing it when possible can help staff | | | | overflowing in others. |
| in spending less time handling repeated storage and | | | | 3. Storage Area Networks - SAN - storage area |
| worrying about backup failures. Below are the four | | | | network (SAN) is an architecture to attach remote |
| types of data storage. | | | | computer storage devices (such as disk arrays, tape |
| 1. Networked-attached storage - NAS - An NAS unit | | | | libraries and optical jukeboxes) to servers in such a |
| is essentially a self-contained computer connected to | | | | way that, to the operating system, the devices |
| a network, with the sole purpose of supplying | | | | appear as locally attached. |
| file-based data storage services to other devices on | | | | Although cost and complexity are dropping, as of |
| the network. The operating system and other | | | | 2007, SANs arestill uncommon outside larger |
| softwareon the NAS unit provide the functionality of | | | | enterprises. By contrast to a SAN, Network Attached |
| data storage, file systems, and access to files, and | | | | Storage (NAS) uses file-based protocols such as NFS |
| the management of these functionalities. The unit is | | | | or SMB/CIFS where it is clear that the storage is |
| not designed to carry out general-purpose computing | | | | remote, and computers request a portion of an |
| tasks, although it may technically be possible to run | | | | abstract file rather than a disk block. |
| other software on it. | | | | Historically, data centers first created "islands: of SCSI |
| NAS units usually do not have a keyboard or display, | | | | disk arrays. Each island was dedicated to a application, |
| and are controlled and configured over the network, | | | | and visible as a number of "virtual hard drives" (i.e. |
| often by connecting a browser program to their | | | | LUNs). Essentially, a SAN connects storage islands |
| network address. NAS systems contain one or more | | | | together using a high-speed network, thus allowing all |
| hard disks, often arranged into logical, redundant | | | | applications to access all disks. |
| storage containers or RAID arrays (redundant arrays | | | | Operating systems still view a SAN as a collection of |
| of inexpensive/independent disks). | | | | LUNs and usually maintain their own file systems on |
| NAS removes the responsibility of file serving from | | | | them. These local file systems, which cannot be |
| other servers on the network. A NAS appliance is a | | | | shared among multiple operating systems/hosts, are |
| simplified form of file server. Authorized clients can | | | | the most reliable and most widely used. If two |
| see folders and files. Installation consists of rack | | | | independent local file systems resided on a shared |
| mounting, connecting power and Ethernet, and | | | | LUN, they would be unaware of this fact, would have |
| configuring via a simple browser-based tool. NAS | | | | no means of cache synchronization, and eventually |
| devices are frequently used to consolidate file | | | | would corrupt each other. Thus, sharing data |
| services. To prevent the proliferation of file servers, | | | | between computers through a SAN requires |
| a single NAS appliance can replace many regular file | | | | advanced solutions, such as SAN file systems or |
| servers, simplifying management and reducing cost | | | | clustered computing. |
| and workload for the systems administrator. | | | | Despite such issues, SANs help to increase storage |
| 2. Direct-attached storage - This is the most | | | | capacity utilization, since multiple servers share the |
| common form of server storage. The disks may be | | | | storage space on the disk arrays. The common |
| internal to the server or they may be in an array | | | | application of a SAN is for the use of transactionally |
| that is connected directly to the server. Either way, | | | | accessed data that require high-speed block-level |
| the storage can be accessed only through that | | | | access to the hard drives such as email servers, |
| server. | | | | databases, and high usage file servers. In contrast, |
| The main protocols used in DAS are SCSI, SAS, and | | | | NAS allows many computers to access the same file |
| Fibre Channel. Traditionally, a DAS system enables | | | | system over the network and synchronizes their |
| storage capacity extension for a server, while | | | | accesses. Lately, the introduction of NAS heads |
| keeping high data bandwidth and access rate. A | | | | allowed easy conversion of SAN storage to NAS. |
| typical DAS system is made of one or more | | | | 4. All-in-one networked storage - An all-in-one |
| enclosures holding storage devices such as hard disk | | | | network storage device combines the capabilities of |
| drives, and one or more controllers. The interface | | | | SAN and NAS providing flexibility to businesses. |
| with the server or the workstation is made through a | | | | By combining block and file-level storage, clients on |
| HBA (Host Bus Adapter). | | | | the LAN have direct access to shared files on the |
| Backups must be either performed on each individual | | | | all-in-one device, and application servers share |
| server with a dedicated tape drive or across the LAN | | | | storage. Instead of having to predict how much |
| to a shared tape device, consuming a significant | | | | storage will be required for file sharing versus |
| amount of bandwidth. Storage can only be added by | | | | application data, storage can be allocated from a |
| taking down the application server, adding physical | | | | central pool. |