Hi Carl, welcome to Nimble Connect!
Today we do not allow you to set read-only access to Nimble volumes - and although Veeam have written this in their guides it's more of a nice-to-have need. So in the world of Nimble you just present normal access to your backup server.
Having said that we do have an open RFE (Request for Enhancement) in Engineering to allow read-only access specifically for backup servers. Please speak to your local SE to add your case to the RFE... the more customers ask for it, the higher in priority it's marked.
Carl - Thanks for sharing this info -- it's a very interesting approach. Veeam's recommendation is indeed valid to prevent Windows from accidentally writing NTFS signature on VMFS volume (in the event where auto mount is not disabled) -- you could try this, disable auto mount in the guest, clone the nimble volume of interest, present the cloned vol to the backup proxy and see if there's an adverse effect. If your clone is still in tact after a backup job, then you know this method would work by disabling auto mount. Let us know if that works out for you!
Per Veeam's recommendations, I had already disabled auto mount. I didn't think to clone the volume and connect to the clone. I connected the actual volume (figuring I could restore a previous snapshot if I had to). Everything worked fine, so I'm off to the races!
One thing I wish I'd done earlier - install Nimble Connection Manager (NCM) on all the Veeam Proxy guest VMs. I recently upgraded my Nimble to OS 2.0.7. I then spend quite a bit of time setting up iSCSI connections to each of the 16 volumes I backup. Actually, since I enabled MPIO on each guest, I had to set up 64 iSCSI connections per guest (16 volumes x 4 Nimble iSCSI ports). Times three proxies, that is 192 connections! Then I installed all the Windows hotfixes and NCM on each guest. If I had done NCM first, I could have automated almost all of that work.