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Diskeeper: Three key points not to be over looked in your virtual strategy

April 2011 by Diskeeper Europe

Virtualisation is becoming the omnipresent mantra of which probably every IT dept has heard, uttered and read over the past few years. The bandwagon has well and truly arrived, and you know it’s only a matter of time before management are on you, poking and prodding at your IT strategy, gleefully uttering phrases like “that cloud-back up thing sounds good, why can’t we just do that?”. To cap it off, you are also simultaneously dealing with server upgrades, migrations, endless helpdesk calls and a whole myriad of other problems that are usually thankless in resolution.

Definitely the implementation of virtualizing your entire IT infrastructure is not something to be undertaken lightly. As a very brief and definitely not comprehensive summary this would include:

• Deciding which machines you are going to virtualize (complete or partial).

• Decide on the hardware/software requirements based on the virtual platform you are migrating to, example “Hyper-V”, “VMware” or “Xenapp”.

• Build the platform starting with a few servers/workstations and test it thoroughly - performance and resource consumption.

• Build proper backup for redundancy/failures and setup tools to monitor and correct performance issues.

Of course the benefits speak for themselves; hardware reduction, central management, operational savings and even the environmental benefits - less power consumption (or hardware pollution we could affectionately call it). The ramifications from implementing a virtual environment are manifold. But what are the negative aspects?

Every resource in a virtual platform is shared, especially the underlying Hardware (CPU, memory etc). The virtual machines on the host are not aware of other guests sharing resources on the same host, which would lead to competition among the guest machines, when general house-keeping tasks like AV scans, defragmentation are run at the same time on all the machines. In general all resource intensive tasks if kicked off on all the guests at the same time would affect the performance on the host. Another drawback is, in a virtual platform if the performance on one machine is affected, it affects that machine as well as all others sharing the same host.

There are three vital points which are easily over looked:

1. I/O bottlenecks and performance degradation created by accelerated fragmentation ―the action of breaking up a file into pieces and writing it to scattered locations on the disk― in virtual platforms.

2. Virtual disks that are set for dynamic growth don’t shrink again when data is deleted. They waste the free space instead.

3. Virtual machines compete for shared I/O resources and their use is not effectively prioritized across the platform.

These barriers would result in lower performing virtual machines and defeats the whole purpose of migrating to a virtual platform. Optimizing the systems and doing it without resource conflicts is the remedy. Removing fragmentation at the file system level would result in lesser I/O’s generated, avoiding unnecessary excess/split I/O’s sent to the disk subsystem. Lesser I/O requests result in greater standards for I/O performance and reliability.

"One of the key areas to any good virtualization project is performance optimization. Some folks tend to focus their optimization efforts around CPU and memory, but fail to consider the effects that virtual machines and file fragmentation can have on a virtual environment. Defragmentation can help considerably with disk latency issues and relieve many of the pressures and bottlenecks associated with consolidating disk I/O channels." David Marshall,

Disk space is a valuable resource and any space wasted in a virtual environment is totally unacceptable. Continuous monitoring of the space used, especially in a dynamic environment is needed and any unused space within the volumes must be returned back to the available pool to be used by other machines requiring it.

Better performance and better storage space utilization are both elements of the efficiency promised by virtualization. Sharpening efficiency in both of these areas can result in off-the-charts delivery on the virtualization promise. V-Locity, a virtual platform disk optimiser provides a comprehensive solution to the virtual short comings listed above.

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