Fragmentation is three times as destructive in virtual environments
1 min read
Just as fragmentation has a detrimental effect in physical windows machines, so it does in a virtual environment, but the effects can be three times as damaging.
That's the warning from Naveen Louis, tech support specialist at Diskeeper, who explains that the problem arises because fragmentation happens at different levels.
"There are three levels of virtualization that relate to a virtual hard disk," he says, explaining these as the virtual hard disk on the guest virtual system, virtualisation mapping data, and the virtual hard disk file.
"Fragmentation occurs at all these three levels of virtualisation: on the virtual hard disk on the guest virtual system, when mapping the virtual hard disk data to the physical virtual hard disk file, and on the physical virtual hard disk file residing on the host system," states Louis.
"The files users' accesses are saved as normal files in the VHD [where] these files are more likely to be fragmented as the underlying file system is NTFS," he states. "The logical addresses of these fragments are then mapped to the physical location on the host disk.
"The VHD, which is a file in essence, will also get fragmented over time on the host disk. In short, we have fragmentation within fragmentation and in a virtual environment we need to 'pass through' several layers before we touch the data stored on the physical disk."
Louis also makes the point that, if these files are fragmented it would increase the delay and affect the overall performance of not only that guest but all other guests sharing the same host.
For him, the solution is to address fragmentation at all levels: if the host is running windows, then it, too, needs to be defragmented, while if it is Unix based, the detrimental effects are less important.
