Is there a way to add an external USB HDD that is connected to my Netgear Rangemax router via USB to ESXi 4.0 as a datastore? The external is formatted as NTFS and I have data on it already.
Can the NAS expose the drive via either iSCSI or NFS? If so, yes. Be prepared for awful performance, though. You'll be using a desktop-class hard drive, connected via USB to an underpowered router that isn't intended to ship around the amounts of data you'll be throwing at it.
I have done this!
Successfully or not, that is the question..
We connected a Buffalo TeraStation over USB to one of the ESX hosts, then connected the device to a Fedora Linux VM, and served up the (pre-existing NTFS contents) as a NAS datastore.
We used it only for VM backups and archives, since the performance was ABYSMAL.
I don't remember exact performance numbers, but it was around 20x slower than the local RAID5 disks in the host, and maybe 100x slower than the FibreChannel SAN.
(I'm vaguely remembering 3MB/sec vs 60MB/sec vs 300MB/sec??)
But it was incredibly useful as a place to stash temporary backups off the SAN during any kind of risky maintenance, and also to transfer VMs between the data center and the office.
(A 2TB disk in a taxi can provide better throughput than a 100Mbit WAN!)