1.Add help text for each field to describe what it's for or what it is showing. This might help people that are new to NetApp.
Great Suggestion. I will try to make it in the next version
2.Is the tool designed to show usable space on just a single shelf, or for an array with multiple shelves?
Multiple shelves. Think interms of no of disks.
3.Is the app assuming that disks are assigned to just a single controller?
Yes. All I am trying to show is an approx space if we buy "n" no of disks
4.Is the app assuming that all disks are assigned to just a single aggregate? I'm assuming so since it's asking for the number of disks assigned to the root volume, which suggests a single aggregate with multiple volumes?
Yes single aggregate.
5.Does the app assume that there is just a two volumes, one for root, and the other needs. I ask since volume reserve only kick in AFTER you've created a volume if I understand correctly? And in that case, under usable space, is it showing the data for the second volume, or just raw disk space. Should there be fields to show the total aggregate space and the total volume space?
I am just trying to make this very simple. I am deducting the root vol disks either 2 or 3 which leaves with one aggregate (basically for other needs).
A few best practices on root volume.
Root volume contains all configurations files (ONTAP Files). It is always preferred to separate the root volume from the data volumes on the filer. For optimal management, it is better to restrict the root volume to just 2 disks (minimum required for a RAID-4 parity group). This enables faster reconstruction times in case of a disk failure on the root volume
Refer netapp link here - https://library.netapp.com/ecmdocs/ECMM1278325/html/sysadmin/planning/concept/c_oc_plan_root-vol-rec...
6.Assuming that the app is splitting the aggregate in to two volumes, if you change the number of disks allocated for root volume, does it then adjust to show data for a single volume
Yes..single aggregate.
7.Does the Raid Group Size Estimater actually change the amount of disk space shown, or is it just to show recommended values for RG size?
No effect on the disk space. Just shows recommended values. Fill the top 3 rows (before the separator line)