Removable Storage provides services to applications and system administrators that facilitate the use, sharing, and management of removable media devices, such as tape drives and robotic storage libraries. The availability of Removable Storage technology eliminates the need for independent software vendors (ISVs) to develop customized solutions and support for these devices on a per-device basis. More importantly, Removable Storage enables multiple storage applications to share expensive removable media storage devices. Thus the focus of storage applications can be directed to customer features rather than hardware issues.
As shown in Figure 14-1, Removable Storage provides a single set of application programming interfaces (APIs) that allow applications to catalog all removable media (except floppy disks and similar small-capacity media), such as disc, tape, and optical media, which are either stored on shelves (offline) or in libraries (online). Also, by disguising the complexities of underlying robotic library systems, Removable Storage lowers the costs of developing and operating storage applications and provides consistency for customers who purchase these applications.
Figure 14-1: Removable media with and without Removable Storage
Removable Storage uses media pools to organize media. Media pools control access to media, group media into media types according to use, allow media to be shared across applications, and allow Removable Storage to track application sharing.
Basic Concepts
Removable Storage can be described in terms of five basic concepts: media units, media libraries, media pools, work queue items, and operator requests. The first item in this list, media, is fundamental and affects all others. The remaining four items in the list are the top-level nodes in the Removable Storage snap-in.
Media Units
Media are classified into media units (also known as cartridges or discs) of a certain type, such as 8mm tape, magnetic disc, optical disc, or CD ROM.
While both sides of double-sided media must be contained in the same library, the state of each side can be different. For example, one side can be allocated, and the other side can be available.
Media Libraries
Removable Storage manages two classes of libraries: online libraries and offline media physical locations. Libraries include both cartridges and the means to read and write them. The offline media physical location is a special holder for cartridges that are cataloged by Removable Storage but do not reside in a library.
Online Libraries
In its simplest form, a library consists of the following components:
A data storage cartridge
A means of reading and writing to the cartridge
For example, a CD ROM drive is a simple library with one drive, no slots, an insert/eject port, and no transport.
In comparison, a robotic-based tape library can hold up to several thousand tapes, have one or more tape drives, and have a mechanical means of moving tapes into and out of the drives.
Robotic library
A robotic library can contain any of the following components: Cartridges, slots to hold the cartridges, one or more drives, a transport, and either a door or an insert/eject port. No user intervention is required to place a cartridge in a library in one of its drives.
Stand-alone drive library
In a stand-alone drive library (also known as a stand-alone drive), the user or a transport must place a cartridge in a drive. The CD ROM drive on most desktop computers is a stand-alone drive library. Removable Storage treats any drive that has an insert/eject port as a stand-alone library.
Offline media physical location
In an online library, the location of a cartridge is the library in which it resides. Cartridges that are not in an online library, such as archived backup tapes on a shelf, are offline media that reside in an offline media physical location. When a user or administrator moves an offline medium into an online library, Removable Storage tracks its location to the library into which it is placed. When a cartridge is taken out of an online library, Removable Storage designates its location as the offline media physical location.
Media Pools
A media pool is a logical collection of cartridges that share some common attributes. A media pool contains media of only one type, but a media pool can contain more than one library. Both sides of a two-sided cartridge are always in the same pool.
Each media pool can control access to the media that belong to it. Although a media pool does not control access to the data that is contained on the cartridges, it does control how the cartridges are manipulated, including an application s ability to move a cartridge from the pool or to allocate a cartridge for its own use.
Media pools can be used hierarchically to hold other media pools or to hold cartridges. An application that needs to group media of several types into one collection can create one application media pool for the whole collection and additional media pools within the original pool one for each media type. A free pool contains a media pool for each media type. Media pools are categorized into two classes: system media pools and application media pools. The system and application media pools are defined as follows:
System pools, which are created by Removable Storage for its own use, include free pools, import pools, and unrecognized pools.
Application pools, which are created by applications to group media, allow several applications to share the libraries attached to a system.
System pools
The following three kinds of system pools hold cartridges when they are not in use:
Free pool. Holds unused cartridges that are available to applications.
Import pool. Temporarily holds cartridges newly placed in a library.
Unrecognized pool. Temporarily holds unidentifiable cartridges newly placed in a library.
Free pool
Free pools support sharing cartridges among applications. The pools contain blank or recycled cartridges that are available to any application. An application can draw cartridges from the free pools, and it can return cartridges to the free pools when the cartridges are no longer needed.
Import pool
When a cartridge is placed in a library, if Removable Storage can identify the format or the application that is associated with it, but has not seen it before, Removable Storage places the cartridge in the import pool. For example, if an administrator places a tape written by Backup on one computer into a library that is attached to a second computer, Removable Storage on the second system recognizes that the tape was written using Microsoft Tape Format (MTF) and places it in the import pool for its media type.
Unrecognized pool
When a cartridge is placed in a library, if Removable Storage cannot identify the format or the application that is associated with it and has not seen the cartridge before, Removable Storage places the cartridge in the unrecognized pool for its media type. Blank cartridges are treated this way. Cartridges in unrecognized pools might have data on them, but Removable Storage cannot read data on these cartridges and cannot catalog them. Cartridges in the unrecognized pool are not available for backup media. Instead, they must be moved to the free pool to be used by Backup. When Backup first starts, it checks the unrecognized pool for media. If media is found there, Backup offers the user the option to move the media to the free pool.
Caution
Moving media to the free pool deletes all data contained on the media.
Application pools
Each application that uses cartridges managed by Removable Storage uses one or more application pools. Applications can create these pools, or you can create them by using Removable Storage. You can set permissions for application pools that allow applications to share pools or that assign each application its own set of pools.
Work Queue Items
When applications make a library request, Removable Storage places the request in a queue and processes it as resources become available. For example, a request to mount a tape in a library results in a mount work queue item, which might wait until a drive or slot is available.
Operator Requests
Sometimes, even with robotic libraries, manual assistance is required to complete a request or perform maintenance. If an application requests that a cartridge in an offline location be mounted, the cartridge must be manually entered into the online library. This generates a request to the administrator or an operator to enter the cartridge.
Available Backup Media
Backup displays a list of all available storage devices in the Backup destination list on the Backup tab. If Backup does not detect any external storage devices, you can back up data to a file on the hard disk. If you want to back up to a medium that Removable Storage does not manage, make sure that you load the medium in the appropriate storage device.
When you back up data to cartridges that are managed by Removable Storage, make sure that Removable Storage is running (you can confirm this in the Services console of the MMC). To back up to new cartridges, first make the cartridges available in the media pool. In an existing media pool, cartridges must be loaded in a library.
Locked Files
In Windows XP Professional, you can back up local files that the operating system locks, such as event logs and registry files. However, Backup skips event logs and registry files if they are open in other applications, and you do not use the shadow copy method to back up files.
To minimize the number of files that are not backed up, it is recommended that you use the default method of backing up files, which uses volume shadow copy technology. If you choose to use another method of backing up files, avoid running applications while Backup is running.
Encrypted Files
Encrypted files remain encrypted when they are backed up. Therefore, it is important to ensure that user keys, particularly the recovery agent keys, are also stored safely on backup cartridges. The Certificates console provides methods for exporting keys to floppy disks or to other removable media so that they can be secured.
For information about Encrypting File System (EFS), see File Systems in this book.
Backing Up Files on Your Local Computer
Using Backup, you can back up any file on your local hard disk.
Because most changes on a server occur as users add, modify, or delete files from their computers, it is recommended that you back up changes to users folders daily.
Some users keep most of the files that they want backed up on network shares. Other users require that data on local computers be backed up. Your backup procedures need to take both situations into account.
Network users primarily use applications such as Microsoft Word. You can reinstall the executable files from the original distribution medium, but the time and productivity that is lost doing this make the approach less than ideal. In addition, if you have customized the applications to suit the needs of your organization, reproducing those settings can be more difficult than reloading the programs themselves. Because the applications rarely change, backing them up as part of your backup procedure uses minimal offline storage space and ensures that the latest version is always available.
Backing Up Files on Remote Computers
You can use Backup on any computer to which you can connect remotely. This allows a single-medium drive to be shared across an entire network and one backup policy to be in effect for the entire network.
You cannot back up System State data directly from a remote computer by using Backup. You can back up files and folders on a remote computer only by using a shared folder.
To back up the System State data of a remote computer
Run Backup locally on the remote computer to save the System State data to a file on a shared volume.
Back up the System State data file remotely to the shared volume.
To restore the System State data of a remote computer
Restore the System State data file remotely to the shared volume.
Restore the System State data file locally on the local computer.
