Virtual servers put pressure on backup


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Virtual servers have solved a lot of problems in the data center, but they've also made backup a lot harder. There are several ways to back up virtual servers, each with unique advantages and disadvantages.

Backup is the single biggest gotcha for VMware nirvana in large environments today. The usual backup methods cause many environments to limit the number of virtual machines (VMs) they place on a single ESX server, decreasing the overall value proposition of virtualizing servers. To further compound matters, one possible solution to the problem requires purchasing additional physical machines to back up the virtual machines (VMs).

However, there are existing products that can solve the problem, if you're willing to move your VMware environment to different storage. If that's not possible, there are some "Band Aid" remedies that can help until storage-independent products arrive. However you ultimately address virtual machine backup, you can at least take some comfort in knowing that you're not alone in your frustration.

The problem is physics

Whenever I consider VMware, I find my mind turning to the movie The Matrix. The millions of VMs running inside VMware are very similar to all of the virtual people living inside the movie's matrix. As with the movie, when you plug into the "matrix" -- VMware, in this case -- you can do all sorts of neat things. In the matrix, you can fly through the air; with VMware, VMs can

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"fly" from one physical machine to another without so much as a hiccup. In the matrix, you can learn Kung Fu and fly a helicopter in seconds. In VMware, a virtual machine can run on hardware it was never designed for thanks to the HyperVisor.

But when you die in the matrix, you die in real life because your body can't tell the difference between virtual pain and physical pain. Similarly, VMware can't break the connection between virtual worlds and physical worlds. Although those 20 VMs running within a single ESX system may think they're 20 physical servers, there's just one physical server with one I/O system and, typically, one storage system. So when your backup system treats them like 20 physical servers, you find out very quickly that they're running in one physical server.

Usual solution: Denial

Most VMware users simply pretend their virtual machines are physical machines. In various seminar venues, I've polled approximately 5,000 users to see how they're handling VMware backups. Consistently, only a small fraction of those who have virtualized their servers with VMware are also using VMware Consolidated Backup (VCB). The majority simply use their backup software just as they would with physical servers.

There's nothing wrong with doing it that way. A lot of backup administrators suffer from a "VMware backup inferiority complex" because they think they're the only ones doing VM backups that way. They're actually part of a large majority.

This was first published in August 2009

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