It is possible to create a virtualized environment without using any shared storage, but that limits your ability to use advanced features such as vMotion or high availability (HA). With the many affordable options available, there is no reason to limit yourself. Let's take a look at three different approaches to create a cheap shared storage infrastructure.
First, read about how to use shared storage based on a Network File System (NFS), which is useful if you want to use a network-attached storage (NAS) device or a server to offer the shared storage infrastructure. Next, find out how to create your own iSCSI storage area network (SAN) based on affordable server hardware. Finally, read about the last type of affordable storage: the cheap SAN. Even decent SAN vendors are offering iSCSI SANs for the price of a regular server.
More on VMware storage:
Maximize the efficiency of your VMware storage
What VMware Storage VMotion is, how it works and its benefits
A guide to VMware storage choices and Storage vMotion
Using NFS for affordable VMware storage
A Network File System allows users to share files on a network. The protocol has low overhead, which is why it's been very popular for the past several decades -- especially in Linux and Unix environments. The advantage of using NFS as a shared-storage device is that you can configure it on any Linux-based server for free. All you need to purchase is the hardware on which you will install the NFS service.
NFS-based storage offers a directory where you can store virtual machine (VM) image files. Redundancy is the biggest challenge to setting up an NFS-based shared storage environment. To ensure redundancy, you'll need to configure the NFS service in a high availability cluster. While setting up an NFS service is easy, setting it up in a HA cluster is not, which means this method may not be the best approach for admins unfamiliar with the process.
Using iSCSI for affordable shared storage
Another affordable VMware storage option is accessing storage on a SAN using Fibre Channel or iSCSI. You can embed this iSCSI functionality into a chip on your SAN device, but you can also run it from an operating system, which means you have to pay only for the hardware that will offer the NFS service.
Most distributions of Linux offer an iSCSI target by default. One advantage of using iSCSI is that you can configure it to look like a real SAN environment where different logical unit numbers (LUNs) can be presented directly to the VMs, an option that NFS-based storage doesn't offer.
However, you'll still need to make your setup redundant. That means that you'll need at least two physical servers in a HA cluster, so if one server goes down, the other server can take over.
Cheap storage hardware
While big companies are mostly looking for a high-end SAN infrastructure, it's not the only solution for everyone. If you're just running a few servers and looking for an affordable hardware-based storage with built-in redundancy, you can find several of these products for the price of a common server. The iSCSI protocol is common and mature; it's used to access shared-storage devices; and it's available on SAN filers, which are offered by all major vendors for less than $10,000. Instead of using a SAN, you can use NAS as an alternative.
In the past, a NAS typically offered only file shares (such as an NFS share), while a SAN offered access to shared-block devices over a very fast, dedicated network connection. Current high-end NAS servers often include an iSCSI target as well. Because these devices have become common in the corporate market, most of the bigger players offer them. The advantage of using a high-end NAS is that they are typically built with redundant hardware, making them very reliable. This means you don't need to integrate it in a HA cluster.
If NAS doesn't offer the performance you need, look for a SAN alternative. The benefit of SAN arrays often include many functions that allow you to manage storage more efficiently. A SAN gives admins the ability to use snapshots for easy backup and recovery, as well as mirroring for simple site replication. The problem with these products is that you'll often have to buy an additional license key for these features, so you might end up with an expensive solution after all. Therefore, you're probably better off buying NAS hardware with built-in redundancy.
Regardless of the option you choose, you can be sure that vSphere supports all of them.
This was first published in July 2012