Optical storage

This topic provides an overview and reference guide for IBM^® optical support on the iSeries™ server with the i5/OS™ operating system.

These functions that are unique to optical support:

CD-ROM devices
DVD devices Directly attached optical media library devices
LAN-attached optical media library devices
Virtual Optical devices

The information contained in this topic is intended for the following audiences:

System operators and end users iSeries server operators and end users can use this information as their primary reference for CD-ROM, DVD, optical media libraries, and virtual optical support.
Service representatives can use this information to perform activities as directed by the appropriate optical device service guides.

Optical storage on the iSeries server provides an economical and efficient way to store and retrieve large amounts of information at a high performance level. Optical storage devices offer significant advantages over other high-capacity storages devices, such as tape and microfilm, with faster access times and a hierarchical-type file organization. i5/OS optical storage uses files that are stored in directories and files that are stored in subdirectories similar to UNIX^® or PC-based file systems.

The capacity, price, and performance of optical storage continually improve, and IBM remains committed to providing its customers with these improvements over time. Even as new devices are introduced, the basic methods of accessing optical information remain consistent, as these new storage devices are being added under the current file system interfaces that optical storage programs have used for years.

Optical Storage is any storage method that uses a laser to store and retrieve data from media. Examples of this media are compact disk read-only memory (CD-ROM), digital versatile disk read-only memory (DVD-ROM), digital versatile disk random access memory (DVD-RAM), write-once read-many (WORM) cartridges, and erasable optical cartridges. These are some considerations in the usage of optical storage media:

Table 1. Optical media considerations
Consideration	Reason for use
Durability	Optical media can have a shelf life in excess of 50 years
Archive Storage	Write-once read-many (WORM) optical media can be used to archive large amounts of data. Each sector on the media is only written once when creating and updating files and directories. When a file is changed or deleted, a new version of the file gets written, but the old version still exists on the media. All previous versions of the file remain recorded on the media. This capability also exists on erasable media, but the entire disk may be erased and reused.
Transportability	Optical media written with the Universal Disk Format (UDF) media format can be read with any other industry operating system platform that supports UDF, which is an industry standard file system. Optical Media written with High Performance Optical File System (HPOFS) format can be interchanged with other optical media libraries attached to iSeries.
Random access	Optical devices are random access devices. This facilitates the retrieval of relevant data on demand. File access is independent of the order in which the data was stored. Also, multiple users can access the same volume at the same time.

When you use virtual optical storage, you create and use optical images that are stored on your disk units. These optical images are treated as if they were real optical disk media by the internal file system functions. The term virtual applies to the emulation of the optical media sectors when used by read and write functions. Virtual optical media appear as *DVDRAM media in the volume information attributes.

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