Server Virtualization:
Balancing CPU, Storage
and Networking Demands
Virtualization initiatives often become a balancing act for data center
administrators, who are seeking to achieve the optimal configuration of
CPU, storage, memory, and networking. In this expert E-Guide, brought
to you by SearchServerVirtualization.com and Dell, you will discover
how to balance the storage and networking demands of today’s virtual
environments. Learn how to effectively select the best server
virtualiza-tion hardware and server protocols. Explore the features associated
with VMware ESX Server, and gain insight into why this technology is
the industry’s most frequently deployed virtualization option for server
consolidation.
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E-Guide
Table of Contents
Server Virtualization:
Balancing CPU, Storage
and Networking Demands
E-Guide
Table of Contents:
Choosing the best server virtualization hardware and storage protocols
FAQ: How to select optimal memory, CPU and storage for virtualization
Understanding VMware ESX features
Choosing the best server virtualization hardware and storage
protocols
Rick Vanover, Contributor
Successful virtualization installations involve substantial planning in several categories -- especially networking. In the first installment of this two-part tip, I focus on the current server virtualization hardware configurations for network virtualization infrastructures and their costs.
Server virtualization hardware and networking: past to present
When server consolidation-based virtualization was just getting under way, administrators frequently struggled to address network connectivity. The number of ports for copper networking was driven higher compared with the number for physical servers (physical servers hosted only one operating system).
With VMware installations, for example, it a best practice was to separate role-based network connections on physi-cal media. This meant that the service console (or ESX operating system), vmkernel interface (or VMotion interface) and virtual machine (VM) network traffic (or vSwitches and port groups) resided on separate interfaces.
Furthermore, it was a better design principle for each connection to have multiple interfaces for redundancy purpos-es.
Today, on the other hand, server virtualization hardware has adapted to the needs of virtualized data centers. The most visible change is that many virtualized host hardware now have four built-in Gigabit Ethernet (GbE) ports, such as the popular Dell PowerEdge R900 and Dell PowerEdge R710, among others. Four built-in interfaces is one of the most beneficial installation improvements.
Figure 1
A rear view of a Dell PowerEdge R710 with four built-in network interfaces
Choosing the best server virtualization hardware and storage protocols
While it's a best practice to separate physical interfaces, it is possible to stack roles on adapters --including those on different virtual local area networks to deliver the required connectivity -- at no additional Ethernet cost.
Network virtualization infrastructure costs
In many organizations, cost is the top priority. One way to determine which network virtualization infrastructure is best is to calculate cost per port.
For small- and medium-sized installations, an Ethernet-based storage protocol -- such as Network File System (NFS) or iSCSI -- can be attractive. In the Gigabit Ethernet world, architecting a NFS or iSCSI virtualized storage protocol can drive the cost per port model down. Using interfaces that are built into servers or added at a nominal cost compared with Fibre Channel interfaces reduces the cost per port on virtualized servers substantially.
Also, from a cost perspective, switching equipment for GbE is more attractive than Fibre Channel-based switching. With VMware installations, for instance, if you use an Ethernet-based storage protocol, I recommend deploying an iSCSI storage protocol so that the vStorage Virtual Machine File System can be used.
FAQ: How to select optimal memory, CPU and storage for
virtualization
Edward Haletky
Virtualization makes use of four resources: CPU, disk, memory, and network, all of which create a difficult balancing act for data center administrators trying to achieve the optimal configuration for their virtual environment.
How do you select the "best" memory, CPU and storage for virtualization? These answers to frequently asked questions will guide you in your decision-making.
Are there tools to optimize or balance virtualization utilization?
Some hypervisors have tools such as VMware Dynamic Resource Scheduling that automatically detect contention and migrate virtual machines to other hosts to affect an automated balance. There were even hints at VMworld 2009 of this happening for storage contention as well (Dynamic Resource Scheduling using Storage VMotion). Other than the tools provided by VMware for their own products, I have yet to see an automated tool for the other hypervisors.
Should there be more than one virtual CPU for a Virtual Machine?
In general, no, as most applications and operating systems do not actually make use of the other CPUs. There are always exceptions to this statement, and those pertain to those applications that are threaded or have many processes that make them up. Often SQL Server, Exchange, and Terminal Service applications are candidates for multiple virtual CPUs.
Is there a 'best' CPU for virtualization?
This has been a debate for sometime: do I use AMD or Intel CPUs? The answer is use what works best for you. If you have only AMD, go with AMD, etc. The key however is to use CPUs that have either AMD-V or Intel-VT technologies within them. All Quad Core CPUs have this functionality. The other factor to be aware of is that you may require specific processors to meet the functional requirements of the hypervisor. For example, VMware' Fault Tolerance requires a limited subset of CPUs. In general, however, Quad-Core CPUs is the starting point for which CPUs to choose.
How do you select storage for virtualization?
To select storage for virtualization you need to determine what type of storage your hypervisor supports, then look into those options. For example, you would not want a CIFS storage device for VMware ESX.
Once you've done the research, it's time to run tests using your virtual machine workload. Each workload for each company will be different. Therefore you need to design and run your own tests to decide which technology works best and which vendor offers the best set of features for your needs.
FAQ: How to select optimal memory, CPU and storage for virtulization
In general, your storage choices will depend on the speed of your networking adapters. A 12Gb FC-HBA is faster than a 10Gb network adapter, yet a 4Gb FC-HBA will be slower than a 10Gb FCoE adapter. It is important to look at all aspects of your storage.
How do you determine how much memory is in use by your virtualization host?
This is done by looking at the state of the virtualization host. You can go to each VM and do the math, but each hypervisor intimately knows all memory in use. VMware ESX and ESXi optimize memory usage by using transparent page sharing which improves overall virtual memory usage and virtualization memory management.
How do you determine CPU performance?
Since the hypervisor knows every clock cycle given to a specific VM, you can determine CPU performance by looking outside the VM at the hypervisor level. Tools run from within a VM are more a gauge without the ability to give you valid real numbers. The only time when this gauge is real is when the hypervisor has not overcommitted CPU. If CPU overcommit occurred, then each VM is getting a slice of a CPU and not the full CPU which the internal to the VM performance meters require.
Understanding VMware ESX features
David Davis, ContributorVMware's ESX Server is the industry's most widely deployed virtualization option for data center consolidation and server consolidation. In this guide to VMware ESX, we outline the core features of VMware ESX and explain the key differences between ESX and ESXi.
The VMware ESX hypervisor is installed on a physical server that enables a server to run multiple guest virtual machines (VMs) inside it. Each of these VMs then runs as a guest OS, such as Windows Server 2008 or Linux. In this guide to VMware's ESX Server, we explain the core features of VMware ESX Server.
VMware virtualization's hypervisor was recently upgraded from ESX Server 3.5 to ESX Server 4.0. In doing so, VMware's enterprise virtualization platform was renamed from VMware Infrastructure to vSphere. Now, if you want to use ESX Server, you don't buy ESX Server; you buy the vSphere suite, where the exception is the free edition of VMware ESXi. (Learn more about vSphere pricing and upgrading ESX to vSphere.)
Today, vSphere offers two flavors of ESX: ESX (full or classic) or the thin ESX, "ESXi" (installable or embedded). ESXi Server offers the same performance as ESX Server (full or classic editions), but it lacks the service console for command line management. ESXi comes as a free edition and as an installable embedded commercial edition included in vSphere.
Unlike VMware Server or Workstation, VMware ESX Server you install VMware ESX directly on a physical server. Because ESX Server is the operating system and it has a limited set of drivers, you must ensure that your hardware is compatible with ESX. To do so, check the VMware Hardware Compatibility Guide before installing ESX Server.
Core features of VMware ESX:
• Memory overcommittment and deduplication, which allow for higher consolidation ratios
• Huge scalability with up to 64 logical processing cores, 256 virtual CPUs, and 1 TB of RAM per host, enabling higher consolidation ratios;
• Memory ballooning; • Network traffic shaping;
• Network interface card teaming (or NIC teaming);
• VMware vSphere client allows for easy graphical user interface management; • VMware Power command-line interface (or PowerCLI) and vCLI;
• and many more
Understanding VMware ESX features
