Q. What are some best practices for designing iSCSI redundancy for Hyper-V?

A. Are you struggling with all the options available in creating iSCSI redundancy? You’re not alone, because there are many options a and in some cases they're challenging to understand. However, there are a set of best practices that you should know if you’re building a Hyper-V environment atop iSCSI. In Chapter 2 of my recent book The Shortcut Guide to Architecting iSCSI Storage for Microsoft Hyper-V, which is available for download here, I outline a list of best practices that you might find useful:

  • Traditional NIC teaming is not considered a best practice for storage connections.
  • Some storage devices don't support the use of multiple connections per session (MCS). In these cases, your only option is to use Multipath I/O (MPIO).
  • Use MPIO if you need to support different load balancing policies on a per-LUN basis. This is suggested because MCS can only define policies on a per-session basis, while MPIO can define policies on a per-LUN basis.
  • Hardware iSCSI HBAs tend to support MPIO over MCS, as well as including other features such as Boot-from-iSCSI. When using hardware host bus adapters (HBAs), consider using MPIO.
  • MPIO isn't available on Windows XP, Windows Vista, or Windows 7. If you need to create iSCSI direct connections to VMs, you must use MCS.
  • While MCS does provide a marginally better performance than MPIO, its added processor utilization can have a negative impact in high-utilization Hyper-V environments. For this reason, MPIO may be a better selection for these types of environments.

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