User`s guide

PLANNING FOR HYPER-V
November09 Page13 
disks among the controllers and modify them to balance I/O access so as to balance
controller utilization.
Layer3Optimization
Differentiated Services (DiffServ) provides a good method for managing your
network traffic. Some switches have a proprietary implementation of this that is
called Quality of Service (QoS). DiffServ uses the Differentiated Services Code Point
(DSCP) to distinguish between service levels of each IP connection. These service
level agreements are on a Per-Hop Basis (PHB). As such, within the internal
corporate network traffic flows can be predictable, but after a WAN link leaves the
company, the service agreements are no longer valid. Four levels are typically used
with DiffServ.
1. Default PHB – Typically this level is best-effort traffic.
2. Expedited Forwarding (EF) PHB – Good for low-loss, low-latency traffic.
3. Assured Forwarding (AF) – Behavior group.
4. Class Selector PHBs – Maintain backward compatibility with the IP
precedence field.
To choose what service level to use, examine the needs of the applications
connected to the storage array. For instance, if you have your servers set up to
iSCSI boot, or are using virtualization to “hide” the storage array (and the guest OS is
booting off a C: drive that is actually on the storage array), select EF because the
data must get to the server and, if there is latency, the server locks up. On the other
hand, you might want all of your traffic coming in from the Worldwide Web set to the
lowest possible class of AF so the service level does not affect your critical data.
Considerations for Storage and Network Adapters
(Dell PowerVault MD3000/MD3000i Storage Arrays)
When planning for the network configuration, make sure that you have at least two
network adapters assigned for your virtual machine traffic. If you are planning to add
MS-Exchange, MS-SQL, MS-SharePoint, or a similar configuration to your virtual
machines, use two dedicated network connections for each of those applications. For
example, if you have a file server, MS-Exchange, and a SQL server running on virtual
machines, you should have six network connections (two for MS-Exchange, two for the
SQL server, one for the file server, and one for managing the Hyper-V server). For
clustering, have two additional network connections for the cluster heartbeat.
Connecting the Dell PowerVault MD3000 Storage Array
The connection to the Dell PowerVault MD3000 storage array is SAS based. Figure 3
shows how the SAS storage cabling is configured.