What is the best way to backup windows SQL, Exchange or AD servers data to? NAS, external USB , iSCSI or perhaps some other backup solution?
I will not however be considering cloud backup solutions due to bandwidth restrictions and cost.
Currently I find NAS devices to give the best results but clients that do not have the budget for backup software use Windows Server Backup but then they can make only 1 backup to a NAS at a time.
You can not answer this question without knowing more about the specific scenario. There is no "best" way, it depends on the use case. Network topology, location, cost, bandwith, available equipment, size of the network and so on. For a small SOHO it may be best to backup to external USB drives because it's cheap and reliable but you won't see that in a Fortune 500 company...So this question can't be answered without knowing details.
