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4. Chunk size

Holding disk chunk size.

Dumps larger than the specified size will be stored in multiple holding disk files. The size of each chunk will not exceed the specified value. However, even though dump images are split in the holding disk, they are concatenated as they are written to tape, so each dump image still corresponds to a single continuous tape section.

If you specify 0, Amanda will create holding disk chunks as large as ((INT_MAX/1024)-64) Kbytes.

A negative value causes filesystems larger than the absolute value to be dumped directly to tape, without using the holding disk. The default value, -1, is interpreted as -((INT_MAX/1024-64) Kbytes. which causes Amanda to dump filesystems larger than slightly less than 2 Gbytes (assuming 32 bit integers) directly to tape. The default is provided mainly for backward compat­ ibility. You are encouraged to specify a positive value smaller than the maximum file size in the holding disk filesystem.

Each holding disk chunk includes a 32 Kbyte header, so the minimum chunk size is 64 Kbytes (but that would be really silly).

Operating systems that are limited to a maximum file size of 2 Gbytes actually cannot handle files that large. They must be at least one byte less than 2 Gbytes. Since Amanda works with 32 Kbyte blocks, and to handle the final read at the end of the chunk, the chunk size should be at least 64 Kbytes (2 * 32 Kbytes) smaller than the maximum file size, e.g. 2047 Mbytes.

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