| s computing networks typically have very powerful | | | | resources) |
| client computers with significant amounts of captive | | | | The most common form of server storage today is |
| storage attached to each one. Processing power is | | | | still Direct Attached Storage (DAS). The disks may |
| very easily available and the Internet interconnects a | | | | be internal to the server or they may be in an array |
| huge number of private networks and individual | | | | that is connected directly to the server. The storage |
| computers. Captive storage for clients, servers and | | | | may only be accessed through that server. An |
| dedicated applications has exploded. Successfully | | | | application server will have its own storage; the next |
| executed backups and (more importantly) successful | | | | application server will have its own storage; and the |
| restores, may mean the difference between | | | | file and print servers will each have their own |
| gracefully recovering from data loss and starting the | | | | storage. Backups must either be performed on each |
| countdown to seeking new employment. | | | | individual server with a dedicated tape drive or across |
| As processing power proliferates, and dedicated | | | | the LAN to a shared tape device consuming a |
| captive storage follows along with each new | | | | significant amount of bandwidth. |
| machine, storage "islands" are gradually formed. | | | | Storage can only be added by taking down the |
| Islands are dedicated storage arrays or volumes that | | | | application server, adding physical disks and rebuilding |
| are only used by a single host or a single application. | | | | the storage array. When a server is upgraded then |
| One example of a common island is an Exchange | | | | its data needs to be migrated to the new server. |
| server with an external SCSI array; another could be | | | | SAN (Sharing of data resources) |
| a SQL server with some dedicated RAID-protected | | | | A SAN allows more than one application server to |
| drives. Captive locally attached storage for a | | | | share storage. Data is stored at a block level and can |
| database cannot be shared out to other computers | | | | therefore be accessed by an application, not directly |
| nor can it be easily grown, moved or duplicated | | | | by clients. The physical elements of the SAN |
| without placing a significant burden on or even | | | | (servers, switches, storage arrays etc.) are typically |
| causing downtime for the host. | | | | connected with Fibre-Channel. Backups can be |
| These islands represent wasted hardware investment | | | | performed centrally and can more easily be managed |
| dollars, since many times some are underutilized while | | | | to avoid interrupting the applications. The time taken |
| others are overflowing. Also these islands propagate | | | | for backups is dramatically reduced because the |
| over time they increasingly burden the systems | | | | backup is performed over the high-speed SAN and |
| administrators with management of the new growth. | | | | no backup traffic ever impacts users on the LAN. |
| Storage islands often cause backup problems, | | | | The primary advantage of a SAN is its scalability and |
| requiring dedicated tape drives and software to | | | | flexibility. Storage may be added without disrupting |
| manage multiple individual backup tasks - not to | | | | the applications and different types of storage may |
| mention the time and burden on the host when a | | | | be added to the pool. |
| restore is necessary. | | | | Adding storage capacity has become more simplified |
| The benefits of centralized storage are that | | | | for systems administrators, so it is no longer |
| application data can be combined into a single storage | | | | necessary to bring down the application server. |
| device or pool of devices called a Storage Area | | | | Additional storage can simply be added and then |
| Network (SAN). SANs provide very high performance | | | | configured and made immediately available to those |
| data storage that can be scaled as needed. File | | | | applications that need it. Upgrading the application |
| sharing services, usually proved by partially or wholly | | | | server is also simplified; the data can remain on the |
| dedicated servers, can be consolidated into a | | | | disk arrays, the new server just needs to point to |
| Network Attached Storage (NAS) server. A single | | | | the appropriate data set. |
| application server can share files as well as host | | | | The actual implementation of a SAN can be quite |
| dedicated application data, as well as run software | | | | daunting given the cost and complexity of |
| for backup and restore tasks. But as servers grow in | | | | Fibre-Channel infrastructure components. For this |
| capacity while narrowing their specialization, the | | | | reason, SAN installations have primarily been confined |
| advantages of consolidating become clearer. | | | | to large organizations with dedicated storage |
| With increasing pressures of security, regulatory | | | | management resources. |
| compliance and corporate governance, management | | | | The last few years have seen the emergence of |
| of business data is becoming ever more complex and | | | | iSCSI (which means SCSI over IP or Internet |
| important. Technology is allowing organizations to | | | | Protocol) as a new interconnect for a SAN. iSCSI is a |
| create and store exponentially more data; the key to | | | | lower cost alternative to Fibre-Channel SAN |
| being successful is managing that data explosion. | | | | infrastructure and is an ideal solution for many small |
| Consolidation means reducing the amount of time | | | | and medium sized businesses. Essentially all of the |
| spent managing tasks, jobs,applications and data | | | | same capability of FC-SAN is provided, but the |
| growth. Moving all types of data to a single, central, | | | | interconnect is Ethernet cable and the switches are |
| redundant and high-performing storage server could | | | | Gigabit Ethernet, the same low-cost technology that |
| mean less time spent handling repeated | | | | is commonly in use today on most LANs, slightly |
| storage-related tasks and worrying about backup | | | | lower performance but most organizations will not |
| failures. | | | | notice. |
| Direct Attached Storage (No sharing of data | | | | |