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While there are no visible userspace changes when files are compressed, the ‘isi get’ CLI command provides straightforward method to verify whether a file is compressed. If compression has occurred, both the ‘disk usage’ and the ‘physical blocks’ metric reported by the ‘isi get –DD’ CLI command will be reduced. Also, at the bottom of the command’s output, the logical block statistics will report the number of compressed blocks. For example:
Metatree logical blocks:
zero=260814 shadow=0 ditto=0 prealloc=0 block=2 compressed=1328
For more detailed information, the –O flag, which displays the logical overlay, can be used with the ‘isi get’ command. This command is described in more detail later in this paper.