Enabling data deduplication on NetApp ONTAP

By tom on June 18th, 2009

I recently enabled data dedup (previously called a-sis) on our storage boxes for the volumes that contained the vmware guests.

Data dedup is a free option as from march 10, 2008, however it is not enabled by default and you should ask your distributor for the licenses. You will get 2 license keys, one for nearstore (which is a prerequisite), one for a-sis.

You enable the licenses on your filer like this:

license add [your license code for nearstore]
license add [your license code for a-sis]

Once the licenses are entered, you can enable it on a per-volume basis like this:

sis on /vol/[your volumename]

The process normally doesn’t start right away, but runs at midnight. You can however force the process to start immediately by typing following command:

sis start –s /vol/[your volumename]

To view the benefits of the data dedup, you can execute:

df –s /vol/[your volumename]

In my case the deduplication process showed a 57% space saving!


After a day or two, I checked back and now the savings are up to 62% for a first volume (which also contains some .iso files and 2 different types of OS), but up to 80% for a volume that only contains Win2k8 guests!