21 August 2007

Sparse files:

A sparse file is a file that is handled in a way that requires much less disk space than would otherwise be needed. Sparse support allows an application to create very large files without committing disk space for those regions of the file that contains only zeros. For example, you can use sparse support to work with a 42-GB file in which you need to write data only to the first 64 KB (the rest of the file is zeroed). In other words, all meaningful or nonzero data is allocated, whereas all non-meaningful data (large strings of data composed of zeros) is not allocated. When a sparse file is read, allocated data is returned as stored and unallocated data is returned, by default, as zeros. Sparse file support allows data to be de-allocated from anywhere in the file.

If you copy such a file (with sparse file attribute set) to FAT or earlier NTFS version, the file is build to its original size (non-allocated space will be filled up by zeros). If the required space is not available, the operation does not complete. Paragon NTFS for Linux driver fully supports NTFS sparse files with sparse file attribute set.

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