Sunday, November 30, 2008

Tips To Avoid Virtual Machine Issues

By Mike White

With the increasing popularity of Virtual Machines comes an issue that many may not be aware of. This problem is an age-old issue that has affected systems from the very early days of storage. It can cause hard drive failure leading to expensive data loss scenarios necessitating data recovery professionals. This problem is, of course, fragmentation.

Just like any other software virtual machines still require (unless you have a very specialist setup) to be run from the hard drive, which is still and probably will remain so for many years to come, the slowest part of your system. Drives can be broken in sub parts know as partitions which can then be utilized as a different drive so to speak but hard disk fragmentation is still an issue.

Fragmentation occurs on all hard drives and is part of the way the operating system stores the data on a disk. It won't lay it down nice and neatly in one continuous block, but will lay it wherever there is a space. One file could literally be split into many separate places on the hard disk and this is fragmentation. If you have one OS running it can be bad but if you are running virtual machines the problems is far more serious.

Fragmentation will not only slow down your computer or server but due to the excessive and unwarranted extra movement of the heads, the life of your storage device(s) can be seriously reduced. The problem is not only limited to single drives however, even if you have a very well specked raid set up, fragmentation can get so severe that the only viable option is data recovery or server rebuild.

Operating systems handle fragmentation in different ways. Microsoft Windows, for example, pays little or no attention to the degree of fragmentation on a storage device, whereas Mac OS X goes some way to helping by automatically defragmenting files under 20 MB in size. Other Operating Systems handle file fragmentation in various ways, with varying levels of success.

Defragmentation utilities can take care of this problem, however, running them practically ties up the machine until completion, slowing the machine to a crawl. So what can be done to remove this issue? There are a number of possibilities that can be tried.

Use automated defragmentation routines: Dependent upon your OS you can normally, either directly in the OS itself or via third party software; schedule defrags to run at times convenient to yourself.

Invest in dedicated hardware. Not the cheapest solution but for business and power user home systems probably the most sensible route. Dedicated hardware could be an additional hard drive (internal or external) a dedicated raid array or even an SSD device. The actual solution will depend on how mission critical the application actually is.

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