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Windows Server 2012 : A complete virtualization platform (part 7) - Enhanced quality of service

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1/23/2014 2:46:59 AM

4. Enhanced quality of service

In the section titled Hyper-V extensible switch,  we looked at the new bandwidth management capabilities found in Hyper-V, which allows for guaranteeing a minimum amount of bandwidth and/or enforcing a maximum amount of bandwidth for each VM running on a host. This is just one example, however, of the powerful new bandwidth management capabilities built into Windows Server 2012. The term quality of service (QoS) refers to technologies used for managing network traffic in ways that can meet SLAs and/or enhance user experiences in a cost-effective manner. For example, by using QoS to prioritize different types of network traffic, you can ensure that mission-critical applications and services are delivered according to SLAs and to optimize user productivity.

As we’ve previously seen in the earlier section, Hyper-V in Windows Server 2012 lets you specify upper and lower bounds for network bandwidth used by VMs. This is an example of software QoS at work where packet scheduling is implemented by the operating system. But Windows Server 2012 also supports implementing QoS through the use of network adapter hardware that use Data Center Bridging (DCB), a technology that provides performance guarantees for different types of network traffic. DCB is typically found in 10 GbE network adapters and certain kinds of switching fabrics.

The enhanced QoS capabilities included in Windows Server 2012 are particularly useful in shared cloud environments, where the cloud provider wants to ensure that each customer (or business unit for shared private clouds) is able to access the computing, storage, and network resources they need and have paid for or been guaranteed. Customers (and departments of large enterprises) need predictable performance from applications and services they access from the cloud, and the enhanced QoS capabilities in Windows Server 2012 can help ensure this.

But these enhanced QoS capabilities also can provide benefits to the cloud provider. Previously, to ensure that all customers accessing a shared cloud have enough computing, storage, and network resources to meet their needs, cloud providers often overprovisioned VMs on the hosts in their datacenter by running fewer VMs on more hosts, plus extra storage and network resources to ensure that each customer has enough. For example, the cloud provider might use separate networks for application, management, storage, and Live Migration traffic to ensure that each type of workload can achieve the required level of performance. But building and managing multiple physical networks like this can be expensive, and the provider may have to pass the cost on to the customer to ensure profitability.

With the enhanced QoS capabilities in Windows Server 2012, however, cloud providers can ensure that SLAs are met while using their physical host, storage, and network resources more efficiently, which means cost savings from needing fewer hosts, less storage, and a simpler network infrastructure. For example, instead of using multiple overlapping 1 GbE networks for different kinds of traffic, the provider can use a single 10 GbE network backbone (or two for high availability) with each type of traffic carried on it being prioritized through the use of QoS policies.

From the perspective of enterprises wanting to build private clouds and hosting providers wanting to build public clouds, QoS allows replacing multiple physical networks with a single converged network carrying multiple types of traffic with each traffic type guaranteed a minimum amount of bandwidth and limited to a maximum amount of bandwidth. Implementing a QoS solution thus can save enterprises and hosting providers money in two ways: less network hardware is needed and high-end network hardware such as 10 GbE network adapters and switches can be used more efficiently. Note, however, that the converged fabric still needs to be carved up into Management and Production networks for security reasons.

The bottom line is that the old approach of overprovisioning the network infrastructure for your datacenter is inefficient from a cost point of view and now can be superseded by using the new QoS capabilities in Windows Server 2012. Instead of using multiple physical network fabrics like 1 GbE, iSCSI, and Fibre Channel to carry the different kinds of traffic in your multi-tenant datacenter, QoS and other enhancements in Windows Server 2012 now make it possible to use a single converged 10 GbE fabric within your datacenter.

Implementing QoS

There are a number of different ways of implementing software-based control of network traffic in Windows Server 2012. For example:

  • You can configure Hyper-V QoS as described previously by enabling bandwidth management in the settings of your VMs to guarantee a minimum amount of bandwidth and/or enforcing a maximum amount of bandwidth for each VM.

  • You can use Group Policy to implement policy-based QoS by tagging packets with an 802.1p value to prioritize different kinds of network traffic.

  • You can use PowerShell or WMI to enforce minimum and maximum bandwidth and 802.1p or Differentiated Services Code Point (DSCP) marking on filtered packets.

There are additional ways of implementing QoS as well. The method(s) you choose will depend upon the network infrastructure you have and the goals that you are trying to achieve. See the “Learn more” section for more information about QoS solutions for Windows Server 2012.

In terms of which QoS functionality to use in a given scenario, the best practice is to configure Hyper-V QoS for VMs and then create QoS policies when you need to tag traffic for end-to-end QoS across the network.

QoS and the cloud

If you are a hosting provider or a large enterprise that wants to deploy a shared private cloud that provides “servers for rent” to customers or business units, there are several ways that you can configure Hyper-V QoS to assign a minimum bandwidth for each customer or business unit that access applications and services from your cloud:

  • Absolute minimum bandwidth In this scenario, you could set different service tiers such as bronze for 100 Mbps access, silver for 200 Mbps access, and gold for 500 Mbps access. Then you can assign the appropriate minimum bandwidth level for customers based on the level of their subscription.

  • Relative minimum bandwidth In this scenario, you could assign different weights to different customer workloads such as a weight of 1 for normal priority workloads, 2 for high-priority workloads, and 5 for critical-priority workloads. Then you could assign a minimum bandwidth to each customer based on their workload weight divided by the total weight of all customers accessing your cloud.

Note that minimum bandwidth settings configured in Hyper-V QoS are applied only when there is contention for bandwidth on the link to your cloud. If the link is underused, the configured minimum bandwidth settings will have no effect. For example, if you have two customers, one with gold (500 Mbps) access and the other with silver (200 Mbps) access, and the link between the cloud and these customers is underused, the gold customer will not have 500/200 = 2.5 times more bandwidth than the silver customer. Instead, each customer will have as much bandwidth as they can consume.

Absolute minimum bandwidth can be configured using the Hyper-V Settings in Hyper-V Manager. Absolute minimum bandwidth also can be configured from PowerShell by using the Set-VMSwitch cmdlet. Relative minimum bandwidth can be configured from PowerShell only by using the Set-VMSwitch cmdlet.

As far as configuring maximum bandwidth is concerned, the reason for doing this in cloud environments is mainly because wide area network (WAN) links are expensive. So if you are a hosting provider and a customer accesses its “servers in the cloud” via an expensive WAN link, it’s a good idea to configure a maximum bandwidth for the customer’s workloads to cap throughput for customer connections to their servers in the cloud.

Data Center Bridging (DCB)

Data Center Bridging (DCB) is an IEEE standard that allows for hardware-based bandwidth allocation for specific types of network traffic. The standard is intended for network adapter hardware used in cloud environments so that storage, data, management, and other kinds of traffic all can be carried on the same underlying physical network in a way that guarantees each type of traffic its fair share of bandwidth. DCB thus provides an additional QoS solution that uses hardware-based control of network traffic, as opposed to the software-based solution described previously.

Windows Server 2012 supports DCB, provided that you have both DCB-capable Ethernet network adapters and DCB-capable Ethernet switches on your network.

 
Others
 
- Windows Server 2012 : A complete virtualization platform (part 6) - Live Migration without shared storage, Performing Live Migration
- Windows Server 2012 : A complete virtualization platform (part 5) - Improved Live Migration - Live Migration using a shared folder
- Windows Server 2012 : A complete virtualization platform (part 4) - Network virtualization
- Windows Server 2012 : A complete virtualization platform (part 3) - Using PowerShell to configure the extensible switch
- Windows Server 2012 : A complete virtualization platform (part 2) - Troubleshooting virtual switches, Additional capabilities
- Windows Server 2012 : A complete virtualization platform (part 1) - Hyper-V extensible switch - Configuring virtual switches
- Windows Server 2012 : Deploying domain controllers using Windows PowerShell (part 4) - Verifying domain-controller deployment
- Windows Server 2012 : Deploying domain controllers using Windows PowerShell (part 3) - Additional domain controller in domain
- Windows Server 2012 : Deploying domain controllers using Windows PowerShell (part 2) - Using Windows PowerShell to deploy domain controllers - First domain controller in new forest
- Windows Server 2012 : Deploying domain controllers using Windows PowerShell (part 1)
 
 
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