File Storage

File Storage

Most networks have some form of centralized file storage. For many years, companies have used the online storage approach to file storage. In the online storage scenario, data is stored on hard disks that are accessible on demand. The files that can be accessed on a server are limited to the amount of available hard drive space. Hard drives are fast, but even with drive prices decreasing in recent years, the cost to store a megabyte of data this way is still fairly high. Hard drives have another disadvantage; that is, generally, they cannot be removed for off-site storage or exchange or simply to build a library of files that are seldom required but must be fairly readily available.

Almost all companies have large amounts of infrequently used data. For example, there is usually no need to keep all the financial reports from the previous year online. However, those reports must be stored somewhere in case questions arise or an audit occurs.

Another common approach to file storage, therefore, is offline storage, which consists of removable media that is managed manually. After data is written to a tape or optical disk, the storage medium can be removed from the server and shelved. Users who require offline data might need to know which tape or optical disk to request. Some systems provide indexes or other aids that make requesting the proper offline storage element automatic. A system operator still has to retrieve the tape or disk and mount it on the server, however.

When the slow response of offline storage is unacceptable, a near-line storage approach may be selected. Near-line storage employs a machine, often called a jukebox, to manage large numbers of tapes or optical disks automatically. The proper tape or disk is retrieved and mounted by the jukebox without human intervention. With near-line storage, huge amounts of data can be made available with only slight delays, but at a much lower cost than would be required to store the data on hard drives.