"You need permissions to perform this action" copying file to storage gat.

My name is Brian and I am with the Storage Gateway team.

If this was a timeout for the session in Windows I'd expect more of a semaphore timeout error. Since you mentioned that this is writing for a few minutes then errors out I would rule out Active Directory permissions.

With the behavior described it would sound more like the gateway is denying the write because the cache is full which the gateway would return as an I/O error but some applications may show as permissions.

Can you check the metrics/monitoring tab in the Storage Gateway web console and see what the Cache Percent Dirty metric is at the times you get that error? If it's 90% or greater then it would mean you are writing to the gateway faster than it can upload.

If that is the case you would need to add more cache disk(s) to the gateway (do not modify or remove existing cache disks only add new ones) or increase the amount of bandwidth available to the gateway for uploads.

Thank you Brian, I think you are right. The problem is the cache as I have some dirty cache peeks during those copies.