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Windows XP Backup

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by nbalmaceda

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Im having an HP Surestore DAT 24 external tape drive and using Windows XP Pro Backup utility to back up a disk with 20GB of data. Backup works fine but after it reaches the 12 or 13 GB mark, a message will pop out that the "media is full, please insert a new tape". Im using 24 GB DDS3 tape and compression is set to 2.22 to 1 as confirmed by the HP Storage Works utility. Please help.

6 replies

by toivo talikka

What you experience is just a normal tape full situation.

HP Surestore DAT24 DDS3 tape drive has the capacity of 12GB/24GB. This means 12GB uncompressed and 24GB compressed.

In practice the compressed capacity depends on the nature of the data. Textual data can be compressed all right, but if you are backing up binary data like programs or zipped folders, they cannot be compressed any further and the actual compression ratio is much lower.

by thechas

Just an added note:

File types that are already compressed, or "tight" to begin with actually take up more space when compressed than when just directly copied.

All compression processes add some amount of extra recovery bits to each compressed file. At a bare minimum, checksum data is added to each file to verify data integrity.

Compressed image formats such as JPEGs, CAB, ZIP files, and most executable files actually take up more space when compressed than they normally do.

A zip archive of a self extracting executable is often 15% larger than the self extracting file by itself.

Wave files may compress, MP3 and most other AV formats will not.

The amount of actual compression will vary with the type of files stored.

Chas

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