| "Out of sight, out of mind" can be an interesting | | | | maintain their own file systems on them. These local |
| phenomenon. An example of this is a large piece of | | | | file systems, which cannot be shared among multiple |
| furniture, such as an armoire, that's been standing in | | | | operating systems/hosts, are the most reliable and |
| a hallway for years and causing people to curse and | | | | most widely used. Thus, sharing data between |
| move around it, or bumps their toes or their heads | | | | computers through a SAN requires advanced |
| as they rushed by. Finally someone in the household | | | | solutions, such as SAN file systems or clustered |
| gets fed up and has the armoire moved out of the | | | | computing. Despite such issues, SANs help to increase |
| hallway and into the garage. Problem solved! | | | | storage capacity utilization, since multiple servers |
| Or is it? Just because that bulky armoire has been | | | | share the storage space on the disk arrays. |
| moved doesn't mean it isn't taking up the exact | | | | SAN was seen as a brilliant way to move much of |
| same amount of space; it's just doing it somewhere | | | | this traffic off of servers, which it was and is. |
| else. Someday in the not-too-distant future | | | | Because stored data does not reside directly on any |
| somebody's going to get mad because they've been | | | | of those servers, server power is now used strictly |
| having trouble getting the car into the garage and | | | | for business applications and network capacity is |
| probably yell at the person who moved the armoire | | | | freed up for other purposes. |
| there. It's still causing the same problem! | | | | But a SAN still consists of disk drives. Fragmentation |
| In the computer world, file fragmentation has always | | | | is still very much a performance-crippling problem on |
| been a serious problem needing to be constantly | | | | those drives, and (in a similar way to that armoire) |
| addressed. When it comes to servers, fragmentation | | | | just because it got moved off the network does not |
| becomes much more of a problem simply due to the | | | | mean that it isn't there. In fact, because there are |
| high number of files being created, modified and | | | | additional steps to requesting and accessing files from |
| deleted by multiple users. Fragmentation not only | | | | a SAN, fragmentation can even have more of an |
| increases dramatically but it also impacts a wider | | | | impact from the SAN than from a local or server |
| number of people and their production. | | | | drive. |
| In information technology, a storage area network | | | | Utilizing otherwise-idle resources, defragmentation |
| (SAN) is an architecture to attach remote computer | | | | occurs whenever and wherever possible so that |
| storage devices (such as disk arrays, tape libraries | | | | performance is constantly maintained, and there is |
| and optical jukeboxes) to servers in such a way that, | | | | never a negative performance impact from a system |
| to the operating system, the devices appear as | | | | defrag. |
| locally attached. Although cost and complexity are | | | | With some Disk Defragmenters, fragmentation can |
| dropping, as of 2007, SANs are still uncommon | | | | be removed as a problem, and the SAN solution truly |
| outside larger enterprises. Operating systems still | | | | works as it intended. Unlike the armoire in the garage, |
| view a SAN as a collection of LUNs, and usually | | | | it is completely gone. |