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Defragmentation and SVS?

Created: 30 Oct 2006 • Updated: 29 Jul 2010 • 8 comments
hamletv's picture
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Q:
Does disk defragmentation affect SVS Layers?

-Hamlet

A:
Hi Hamlet. Good question.

The answer is similar to the one we gave in response to the question about disk imaging.

Defragmentation works below the file system. And, since SVS sits above the file system, neither has any affect on the other.

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riva11's picture

I have installed as SVS layer the Google Earth. This program has a very big cache on the disk and I hope that disk defragmentation affects also this area disks where SVS layers is stored.

Paolo

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Scott Jones's picture

Sorry, I sometimes have trouble phrasing things correctly when answering these types of questions.

- SVS layers are data in blocks on the hard drive

- Defrag tools work on data in blocks on the hard drive -- all data in all blocks on the hard drive (except those marked unmovable by the OS)

- Therefore, defrag tools work with SVS layers because they do not (and cannot) know or care that those data blocks happen to contain bits that are in an SVS layer

- It's like two workers in a skyscraper; one on the 10th floor and one on the 20th floor... they both do their jobs, in the same building, but neither has any idea that the other exists

Scott Jones
Product Manager
Altiris, Inc.

Scott Jones
Business Critical Engineer, Endpoint Virtualization
Symantec Corporation
www.symantec.com
 

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riva11's picture

Scott,

Many thanks for your clear description.

Regards
Paolo

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arjain's picture

Hi,
Windows Defrager will not have any effect on SVS layers, but what if i virtualize any software like Diskeeper (Deframentation tool) and defrag my hdd with the virtualize defragmentation software? Will there be any change made after deactivating the layer? Changes made due to a layer are not displayed after layer is deactivated, what will be its effect here?

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Scott Jones's picture

Per Randy Cook (the guy who invented this stuff), a defrag tool running from a later should defragment normally. The reason is that MS provides a defrag API. So when Diskeeper is moving blocks around, it is not doing File Open operations and other standard file system stuff that SVS would redirect.

That being said, this is untested and not recommended. As we've indicated in several other tips, FAQ responses and comments here, certain system tools should rightly have a neutral view of the system, so should be installed in the base and possibly added to the Ignore Process list.

Scott Jones
Product Manager
Altiris, Inc.

Scott Jones
Business Critical Engineer, Endpoint Virtualization
Symantec Corporation
www.symantec.com
 

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hamletv's picture

Thanks to all for answering my question and making everything very clear for us.

-Hamlet

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mb773's picture

Ok, as I see the SVS layers after certain time will be affected by waste space and not chance to defrag...

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Scott Jones's picture

No. That's what I was trying to explain in this comment above. Files in SVS layers do get defragmented. SVS does not affect how defrag works.

Scott Jones
Business Critical Engineer, Endpoint Virtualization
Symantec Corporation
www.symantec.com
 

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