If you're a virtualization administrator setting up an ESXi environment, you know you need to consider how to organize storage. There are many options available with pros and cons to each, but the virtual machine image files should be readily accessible if the host server fails. Here's how to configure some peace of mind into your ESXi storage.
After deciding on a storage device, how do you present it? There are three choices: NFS, iSCSI and Fibre Channel.
To store virtual machine image files, VMware works with data stores. When setting up ESXi, the easiest approach is to use a local data store; in that case, you'll just need one server to set up a virtual environment. This isn't wise because if your sole virtualization server goes down, then you'll have nothing.
To set up an environment that can survive a disaster, store the virtual machine image files on another machine. This can be a server set up as a dedicated storage server, a network-attached storage (NAS) appliance or a high-end SAN product. All three offer the same basic solution, but the price differences are huge.
Choose your storage wisely
For ease and affordability, NAS is probably best, but there are some drawbacks. NAS is like a regular server; it connects to a normal IP network, and you define the types of storage. Within a NAS, some redundancy is available to protect critical items like disks, power supply and network interfaces. But if a NAS fails, you will be left with nothing. If you have decent backups and don't have mission-critical applications, this may not be a problem. But if you require minimal downtime, a NAS may not be the best choice.
Also, storage can be set up on regular servers. Windows as well as Linux operating systems can set up servers as shared storage devices through iSCSI services or NFS file-sharing services. It's more work than setting up a NAS -- which is typically plug-and-play -- but if you are a skilled Windows or Linux server administrator, this is a another option that provides the same service as a NAS.
There's an additional benefit with NAS: You can integrate Linux as well as Windows in a storage cluster. That means if one storage server fails, the other storage server can take over in a matter of seconds.
Another option is to use a storage area network (SAN). This is not just a storage appliance that plugs into your network and is ready to go; it's a storage product that needs its own dedicated network, which will raise the price of your storage system. While a NAS product costs less than $1,000, a typical SAN product will run more than $10,000. You do get some benefit for that extra money -- a dedicated storage box designed to be highly available with a Web interface for easier management.
Presenting storage to the network
After deciding on a storage device, how do you present it? There are three choices: NFS, iSCSI and Fibre Channel. The easiest solution is NFS, which provides shared folders on a network. NFS is a service that comes from Unix and is available by default on all Linux distributions. While it's on all NAS appliances, it's not on Windows, which uses CIFS to create shared folders. VMware ESXi supports NFS shares; all you have to do is create an NFS share on your Linux server or NAS and connect ESXi to it.
The alternative to NFS is using a SAN technology like iSCSI or Fibre Channel. The main difference between a SAN and NFS is that SAN has complete disk devices, whereas in NFS you connect to a share. Because of lower overhead, SAN is typically faster, but in ESXi, you won't see much difference between SAN and NFS.
Another option is iSCSI or the "poor man's SAN." Basically, iSCSI is just SCSI commands encapsulated in IP packets, which means you can run it over a normal network. If you use iSCSI on a dedicated network infrastructure, then you can increase availability to a maximum. Because iSCSI runs on traditional network infrastructure, a network administrator can manage it.
Fibre Channel is the more expensive solution and offers the best possible speed, but most small businesses don't need that type of bandwidth. If you prefer using a ready-to-use appliance, you might find an iSCSI SAN suits your ESXi storage needs.