Backup and restore speed are important considerations when you plan your backup strategy. File-type storage devices such as filesystems or the hard drive back up data more quickly than some tape devices. This feature is especially important if you have a limited time for backup. You can also access your data more quickly during restore operations because filesystems allow random access to your data.
The maximum size of a file-type device on many systems is 2 gigabytes.
Disadvantages of file-type storage devices include expense (disk drives are more expensive than tapes) and the inability to store the data on the file-type storage device offsite.
You must mount and label storage volumes for file-type devices, even though there is no physical volume to mount. When ISM writes data to this file-type volume, the volume is treated as one or more open files. If you enter a value for the file-type volume, ISM writes data to the file-type volume until that value is reached. For specific instructions on how to label storage volumes, see Labeling a Volume.
Although you can specify up to four file-type devices, we recommend a maximum of two file-type devices so that you can reserve two tapes for copying the data. The copying process is called cloning. Once a file-type device is full, you must clone the data to tape before you can overwrite the file-type device with new data. Alternately, you could clone your backups to tape after your backups complete. You must recover the data to the cloned copy on tape. For more information, see Reserving a Storage Device for Cloning and Cloning Storage Volumes.