Server Virtualization in Action: A View From the Trenches – page 3

By Amy Newman (Send Email)
December 30, 2009

- Digg
- DZone
- Reddit
- Slashdot
- StumbleUpon
- del.icio.us
- Facebook
- FriendFeed
- Furl

Deploying Server Appliances

Related to dedicated virtual servers are server appliances. Server appliances are open source (usually) VMs created for a specific function. They are downloadable VM images that serve as web database servers, blog servers, content management system application servers, and even file and print servers, to name a few. They are designed to be smaller and to perform a singular function, which makes them perfect candidates for projects that would otherwise require a physical system that would likely be underutilized.

Server Appliances are ready to use as soon as they’re downloaded, unzipped, and opened in your virtualization software console.

Table 9-4 lists some sites from where you can download server appliances.

Note: Server Appliances must be subjected to the same rigorous security sweeps and pruning as other servers. Donâ€™t trust them just because they are prepackaged.

Adjusting and Tuning Virtual Servers

The next item of business you’ll need to tackle for your dedicated VMs is adjusting and tuning. You’ll need to do this after the system has been up and running for a few weeks so that you’ll have a feel for baseline performance. You need to monitor performance with a performance-monitoring tool such as Orca (http://www.orcaware.com/orca).

Tools like Orca give you a continuous (hourly, daily, monthly, quarterly, and yearly) view into system performance. Not only can you keep an eye on performance peaks and valleys, you can also determine the best times for backups and maintenance. You’ll also know when to add more RAM, more disk, more CPU, or even another VM to share the load.

So how do you tune a VM? The answer is, “almost the same as a physical machine.”

RAM

Adding RAM can be the easiest way to boost performance in physical and virtual systems. Your host system must have sufficient RAM for itself plus enough to run each guest efficiently and have room for growth. Often, but not always, adding more RAM can refresh sluggish systems. RAM is a cheap commodity and it has the highest performance boost per dollar of any performance enhancing adjustment. However, RAM is not always the culprit, as Chapter 12, “Form-Factor Choices and Their Implications,” will discuss, and adding RAM without knowing the root cause could have little impact.

Virtual Machine Add-ons or Tools

Adding your chosen platform’s VM tools is often ignored as a performance- increasing tweak. After installation, even before patching or updating, you should install the VM tools. Your overall experience with the VM’s performance will increase.

Drivers in these tools and add-ons boost and optimize video performance, as well as enhance mouse performance and transitions between host and guest, and deliver time synchronization improvements between host and guest.

Virtual Disks

Virtual drive configuration is also important. Stick with fixed-size virtual disks. Dynamic disks are nice to have, but you take a performance hit when using them. You can always add more disk space by creating another virtual drive for your VM.

Table 9-4 Websites Offering Downloadable Server Appliances.

SITE NAME	URL	DESCRIPTION
Jumpbox	http://www.jumpbox.net	Open source server appliances
ThoughtPolice	http://www.thoughtpolice.co.uk	VMware images of popular open source systems
VirtualAppliances	http://www.virtualappliances.net	Offering specialized open source server solutions
VMware	http://www.vmware.com/appliances	VMware and community server appliances

Virtual Machine Pagefiles and Swap Space

Pagefiles and swap space should be configured as separate drives. This is a bit trickier on Windows systems because you’ll get drive full errors, although they can be turned off. A separate drive for swap space and pagefiles makes your system run more efficiently because it has a separate drive to use for paging. Using a separate partition won’t help performance like it does with physical machines. Using more than one drive for swap space also increases performance. Keep separate swap space drives to 2GB.

Host Machine Performance Tuning

Some system administrators are disappointed with virtualization performance because they assume that purchasing a physical system for their VM host with lots of RAM and disk space is the key to happy VMs. You must build your VM host with virtualization in mind.

CPU

These days most CPUs are designed with virtualization in mind—64-bit multiprocessor host machines should always be used. A two-processor system is good for testing and initial deployment, but for production, you need to use (at a minimum) quad-processor systems. The host machine’s performance should also be monitored closely for those same peaks and valleys. An overloaded host system will result in poorly performing guest systems. Chapter 12 discusses this in greater detail.

RAM

With RAM consumption on the rise for applications and operating systems, there is generally no such thing as too much RAM. Purchase and install the maximum amount of RAM for your host system.

Disks

Drives and drive configuration are often overlooked as a potential performance bottleneck. Drives and configurations should be chosen with care. SCSI drives still outperform even the highest-end IDE drives. Purchase the fastest, widest data transfer rate, highest cache drives you can afford for your host system. One of the biggest complaints against virtualization is sluggish disk I/O. VM disks will never perform like physical disks, but you can ensure that you have the optimum speed available by choosing high-performance drive technology.

Disk Configuration and Controllers

Drive configuration is also very important to performance. The host operating system should be physically separate from any guest machines. Partitions are not good enough. You need to separate them physically on different drives and even different controllers.

Defragmentation and Optimization

On Windows platforms, you should keep your drives defragmented. Fragmentation of a drive, virtual or physical, kills performance. The built-in Windows defragmentation program is good for a start, but if you experience disk lag after defragmenting, get a third-party disk defragmentation and optimization utility. Use it for both physical and virtual systems.

Virus Scanning

Disable virus scanning of your VM environment. You do not need to scan your virtual disk files for viruses. Virus scanning produces a performance hit for virtual disks. If you feel compelled to scan the partition or disk where your VMs live, do a daily sweep of them just before you perform backups.

Server Dedication

Your VM host system should be dedicated to the task of being a VM host with no other jobs. It should not be a mail server, a proxy server, and a file server all in one. Network traffic from your LAN—such as file copying, mail, and disk I/O—has a negative effect on the host’s performance, which is reflected in each running VM.

Network Optimization

Sharing NICs with the host or other VMs has a negative impact on network throughput. Dedicate a physical NIC to each VM where possible, especially where the VM is highly network traffic dependent (such as a web server, application server, or terminal server).

Want to read more than that? Pick up a copy of Practical Virtualization Solutions from InformIT

Follow ServerWatch on Twitter

Page 3 of 3

Previous Page 1 2 3

0 Comments (click to add your comment)

Solid State Drives: The Future of Data Storage?

Solid state disks (SSDs) made a splash in consumer technology, and now the technology has its eyes on the enterprise storage market. Download this eBook to see what SSDs can do for your infrastructure and review the pros and cons of this potentially game-changing storage technology.