First, let me remind you that shared storage is very important to a virtual infrastructure. That’s typically where the virtual machines are stored and it allows many of the advanced features of a virtualization to be possible. If you are building a virtualization lab, very likely you would have some sort of low-end storage area network or network attached storage appliance. You might also have a server that you turned into an NAS or even use a virtual storage appliance which is just a virtual machine that simulates a storage area network (SAN). So, there are 3 different options for share storage. Having a dedicated hardware appliance like a SAN or NAS is going to be the best performance, but also it’s going to cost more than for example, a virtual storage appliance.
It’s unlikely that you’d need shared storage if you just have one ESX, ESXi, or hyper-v Server, but as soon as you go beyond one server you’re going to want to start using features like Vmotion, live migration and vmware high availability. When you get to that point, you might need shared storage.
This is the shared storage appliance I have in my lab. It’s an Iomega X4200D. There’s also a smaller model, the IX2, but I recommend the IX4 because it has space for 4 drives. Both of these models offer iSCSI SAN and NFS.
Here’s a video presentation of this server: