Network Appliance (NetApp) advanced single-instance storage (A-SIS) deduplication is a free technology that ships with every NetApp filer. The technology works at the block level to efficiently compress volumes so that you can get more data in a limited space. All the deduplication setup and maintenance operations are controlled with the sis command. For example, here is the output from sis status:

> sis status
Path                           State      Status     Progress
/vol/vol1                      Enabled    Idle       Idle for 01:17:58
/vol/vol2                      Enabled    Idle       Idle for 14:32:20
/vol/vol3                      Enabled    Idle       Idle for 13:32:33

For some reason, there is no sis command that will reveal how much space the deduplication has created. Fortunately, df -s will take care of that.

> df -sh
Filesystem                used      saved       %saved
/vol/vol0/              2146MB        0MB           0%
/vol/vol1/               883GB      673GB          43%
/vol/vol2/               826GB     1557MB           0%
/vol/vol3/               100GB       40GB          29%

I added the -h to make things a bit more readable.