In some cases, the Fibre Channel or iSCSI connection between a storage array and the Hyper-V hosts may not perform as well as the actual storage array, and the connection can become a bottleneck.
While you are assessing your storage architecture, it is also a good idea to evaluate your storage connectivity. Although some organizations use RAID 5 or RAID 6 volumes, RAID 5 and 6 are poor choices for write intensive virtual machines, because of the overhead involved in writing parity data. RAID 1+0 delivers the performance of striping, with the redundancy of mirroring. Microsoft recommends that this volume be structured as RAID 1+0 (sometimes referred to as RAID 10).
Virtual machine components should reside on dedicated storage, where they will not have to compete with the operating system for storage I/O. The first thing that you should check is virtual machine component placement.
However, there are some other things that you can check to ensure optimal storage performance. In these types of situations, it is usually advisable to move some virtual machines to an alternate Hyper-V host (assuming that local storage is being used). If the I/O demand exceeds (or approaches) the I/O capacity, then performance will suffer. In any virtualized environment, there is a finite amount of storage I/O available, and this I/O must be shared among the virtual machines. This is because there are so many different things that can cause slow storage performance. Poor disk performance tends to be one of the more difficult problems to troubleshoot in a Hyper-V environment. A variety of problems ranging from poor virtual machine performance to issues with high availability can potentially be related to performance. Many of the most common problems that Hyper-V administrators tend to experience are storage related. It is worth noting however, that problems can sometimes have multiple causes, so if you don't initially find any mention of the problem that you are experiencing, then you might try looking in a different section. The solutions presented within this book are grouped by hardware components (storage related problems, network related problems, etc.). For each problem that is discussed, you will find a short description of the problem and one or more step by step solutions to the problem. That being the case, this eBook has been written in an effort to help Hyper-V administrators to diagnose various problems with the hypervisor and Hyper-V virtual machines.īecause it is nearly impossible to discuss every problem that could potentially occur in a Hyper-V environment, this book focuses on the more common problems that Hyper-V admins are likely to encounter.
Although Microsoft Hyper-V is a mature, stable, and reliable server virtualization platform, problems can, and sometimes do occur.
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