defrag strategy for large files

[ddyer]

Defraggler seems to have a very ineffective strategy for defragging large files with lots of fragments. Even when there is lots of free space, it grinds away shuffling files around, while slowly slowly reducing the number of fragments of the current target. Or at least that's the way it looks from the entertainment.

 

I'm sure you get lots of suggestions, second guessing the strategy used. Here's mine. Before you start a defrag

step, calculate a metric for the work you're about to do which weights both the number of megabytes to be moved

and the number of files to be moved. Compare that to the cost of moving the entire file to an open space.

 

Case in point; my primary backup drive has a mix of hundreds of thousands of small files (blame windows and adobe for that) and a few gargantuan files (blame virtualbox for that). It has 25% free space in a 2TB partition. It has taken a week of

defragging to reduce the %fragmented report from 25% to 6%

[mta]

Can't say I've experienced the symptoms you are describing.

I too have a 17gig Win7 vhd and a 5gig XP vhd courtesy of VirtualBox and occasionally 'move to end of drive' which DF does in a reasonable time frame considering the size of the file in question.

 

How big are your gargantuan ones?

What is the gap between running DF? How many files and fragments are we talking?

If it has taken a week of running DF to defrag 1.5TB (2TB - 25% free space) that would indicate something else at play.

Maybe something as simple as a running background task, or as nasty as a faulty HD.

[Andavari]

that would indicate something else at play.

Maybe something as simple as a running background task,

 

Anti-Virus/Anti-Malware software left running in the background can cause it, but a weeks worth is very excessive.

 

I would've bailed out of the defrag long before enduring a full week of it out of fear of over-stressing the hard disk.

[ddyer]

Anti-Virus/Anti-Malware software left running in the background can cause it, but a weeks worth is very excessive.

 

I would've bailed out of the defrag long before enduring a full week of it out of fear of over-stressing the hard disk.

 

I finally did bail out of it when the number of fragments stopped decreasing and the time to finish started going up.

I suspect the defrag algorithm was caught in a hill climbing disaster. I've noticed that occasionaly the number of

fragments reported by the UI temporarily increases.