In sizing Altavault systems, there's a number of metrics to consider, and IOPS isn't usually one of them.
There's the raw ingest rate - ie, how quickly they can absorb backup data. Then there's the rate they can send that data to the cloud, the rate and latency they can retrieve that data and then the rate they can return it.
As this is a backup appliance, it is usually sized in GB/hour, and depending on deployment options and your internet connectivity, it ranges from 175Gb/hr to 3TB/hr - http://www.netapp.com/us/media/ds-3687.pdf
Hope this helps!
