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Data Segmentation, Media File Systems, and DVD Storage Discrepancies
When archiving files and folders, there are several key considerations that account for how the data is segmented into corresponding archive media folders. These include:
Selected Media Type and File System Overhead - When archiving files and folders, a variety of media type options are available for you to use. Selecting any CD or DVD media types will have a bearing on how your data is segmented. To understand how media type selections affect data segmentation, see CD & DVD Media Type Options and File System Overhead below.
DVD Capacity Discrepancies - If archiving to DVD media, there is a common discrepancy between the labeled DVD media size and the available DVD capacity as reported by the operating system (and most applications). To understand DVD capacity discrepancies and how they can affect data segmentation, see DVD Capacity Discrepancies below.
Data Segmentation - Three data segmentation options are available for selecting when archiving to either CD or DVD media. To understand how these options will affect the folders created during the archive operation, see Data Segmentation Concept Diagram and Explanation below.
CD & DVD Media Type Options and File System Overhead
All optical media contain file system information in addition to whatever data is copied to the disk. The size of the file system information that is contained on the disk can vary according to the media type selected, the number of files and folders contained on the disk, and the length of the file and folder names.
The file system written to the disk will vary depending on the media selected (DVD or CD) and whether or not you choose to make a Hybrid disk. Consult the table below for additional information on Media Type selections and the corresponding disk file systems.
Choosing to create a Hybrid disk is an attractive option to many users, as it increases the likelihood that the disk will be readable across a wider array of computer platforms. However, this flexibility comes at a cost: Creating hybrid disks increases the space on the disk devoted to file system information. As a result, hybrid disks provide less space for storing the archived files and folders than are available on non-hybrid disks.
For all CD or DVD formats, the space devoted to file system information increases with the number of files and folders archived to disk, and with the length of the file and folder names. For example, if you want to burn 200 MB of data to disk, the file system on the disk will be larger if that 200 MB is composed of 2000 files and smaller if it is composed of 20 files.
When archiving, Digital Storage ManagerVirtual Ticket Developer will consider the file system overhead of the selected media type when segmenting the data. This can result in more media folders being created than you might initially expect. That the archive media folders created during archiving actually fit the destination media to which they will eventually be copied.
Note: Data segmentation is also influenced by the data segmentation strategy selected and, if archiving to DVD media, by DVD capacity discrepancies. See DVD Capacity Discrepancies and Data Segmentation Concept Diagram and Explanation for more information.
The amount of storage space indicated on a DVD’s label is typically more than the amount of space indicated by the operating system. To understand the difference between labeled/advertised capacity for DVD media and the capacity reported by your operating system, consult the following tables:
The reason for this discrepancy is historical in nature, but it relates to this: The unit of measure used on the label of DVD media is different than the unit of measure used by your operating system. This results in the situation where a 4.7 GB DVD is reported as a 4.38 GB DVD by your operating system. The actual size of the DVD does not change, it’s just that different units of measure are used to indicate the capacity of the same DVD.
Note: The technical term for the unit of measure used by most operating systems is “gibibyte” and is equal to 1,073,741,824 bytes. However, the term “gigabyte” is much more familiar to users and because of this, is the predominant label for 1,073,741,824 bytes despite the fact that such usage is incorrect. A true “gigabyte” is equal to 1,000,000,000 bytes and as such, is somewhat smaller, in bytes, than a gibibyte.
If you have never run into this, try burning 4.4 GB of files (as reported by the operating system) to a 4.7 GB DVD (as indicated on the DVD label). They won’t fit. The reason for this is because two different units of measure are used, even though they both share the same term “gigabyte” (or “GB”).
Similarly, if you try to archive 4.4 GB (as reported by the operating system) of files using a 4.7 GB DVD media type selection, data segmentation will split the files across multiple disks so that when burned to DVD, the archived files and folders will actually fit on the specified media.
Note: It is important to note that CD media labels typically indicate capacity in the same unit of measure as that used by most computer operating systems. The result of this is that the capacity discrepancy that exists for DVD media does not exist for CD media.
When selecting a DVD media type upon archiving, always select the DVD media type that corresponds to the size on the label of the DVDs you will be using when burning the archived files and folders to DVD. If you select a custom DVD size (“DVD Other” or “DVD Other Hybrid” media types), always use the size as labeled on the DVD as your custom size. Digital Storage ManagerVirtual Ticket Developer will convert between the units of measure used on the label and by the operating system to ensure that any data segmentation will accommodate the size of the specified DVD(s).
Note: Data segmentation is also influenced by the data segmentation strategy selected and by the file system overhead for CD and DVD media. See CD & DVD Media Type Options and File System Overhead and Data Segmentation Concept Diagram and Explanation for more information.
Data Segmentation Concept Diagram and Explanation
Choosing different segmentation methods for archiving to removable media will affect how the files and folders are split between disks. The illustration below shows how Digital Storage ManagerVirtual Ticket Developer will separate 4 jobs onto disk for each of the three methods.
Note: All sizes are approximate and used for illustration purposes only. When calculating sizes, the system reserves additional space for file system overhead. This can affect data segmentation. (See CD & DVD Media Type Options and File System Overhead for more information.) Additionally, if archiving to a DVD media type, data segmentation may create more archive folders than initially expected. See DVD Capacity Discrepancies for additional information.
Additional pages related to archiving:
Archiving Using Helper Applications
Archive - Choose Destination Window