Storage Bin 2.0: Virtualization challenges

Ezine

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Backing up and recovering data from virtual machines is easier said than done.


Last month, I used this space to discuss the pervasiveness of virtual machines (VMs) in the data center and how they change practically everything. For many, VMs are a no-brainer value proposition. But let's not forget that the devil is in the details.

If you use VMs within a Fibre Channel (FC) network, you may have a bit of a problem. FC is a Layer 2 protocol and every VM in a physical server shares a common World Wide Name (WWN). That's like everyone in your firm sharing the same phone number or email address--everyone sees everything. FC host bus adapter (HBA) vendors fixed this problem through N_Port ID Virtualization (NPIV), which lets you assign a different WWN to each VM. However, you have to upgrade all of your HBA drivers. No big deal, right? Wrong. iSCSI and NFS don't have this problem because these protocols are IP based and you can assign different IP addresses to your VMs.

Some of the biggest challenges in data centers revolve around backing up and recovering data in a VM environment. There are so many issues to address I could dedicate a book to the topic. Let's look at a select few.

Backup agent in the guest OS:

  • May be burdensome on the host's shared resources, especially if multiple VMs share the same host resources and are scheduled at the same

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  • time.
  • Requires setting up backup scheduling and policies, as well as necessitating a client agent license, for each virtual machine.
  • Lacks bare-metal recovery options, so a VM can't be restored as a whole.
  • Could scramble the VMs and cause performance degradation when the backup process is initiated.
  • Running agents in the guest operating system can lead to backup agent sprawl (a management quagmire).

This was first published in December 2007

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