Recently, LeftHand Networks, one of the original companies focusing on iSCSI storage solutions, released an intriguing new product called the Virtual Storage Appliance (VSA) for VMware ESX. VSA is a product that exposes an ESX server's internal storage as an iSCSI target. Now, you might wonder what is so useful about that. But, consider this: Suppose you have multiple ESX servers, each using direct-attached storage and you simply can't afford a full-fledged SAN--iSCSI or otherwise. Now, suppose you're using these ESX servers in an attempt to make better use of your IT resources, but you're concerned about the "all eggs in one basket" approach you're taking with direct-attached storage.
Enter VSA. VSA is what LeftHand calls a virtual iSCSI SAN. The product makes use of the unused space on your ESX servers to create a clustered iSCSI SAN usable by your ESX hosts. This virtual iSCSI SAN boasts all of the features found in LeftHand's SAN/iQ software, including:
- Thin provisioning (a method by which you can make more efficient use of SAN space by indicating the maximum size of a SAN volume while only actually allocating the space necessary for current data)
So, at a list price of $5,000 per node, VSA for ESX gives your multiple ESX hosts high-availability capabilities, and allows you to make use of features such as VMotion and other VMware high availability features.
In short, VSA allows you to convert your ESX server's direct-attached storage to an iSCSI SAN without incurring any more cost than that of the VSA licenses. Obviously, VSA is only useful if you have at least two hosts so that you can mirror and replicate VM's between the two hosts.
VSA can expose up to 2TB on each ESX host. Further, since the space is exposed via iSCSI, you can create volumes on the ESX hosts that are used by other servers in your environment.
I am currently considering VSA for my organization. I'll report back to you with more information regarding my evaluation, including my overall experience and performance.