Why is multi-thread defragging not possible?

[science man]

Hey guys I googled about multi-threaded defragging and and found this answer. "It's not a limitation of the software. Hard drives aren't designed for parallel processing so multi-threaded defragging isn't really beneficial." But I don't understand, if hard drives aren't designed for it then how do you explain all the other multi-threaded programs out there? (multi-threaded gaming, video converting, ect)

[eL_PuSHeR]

It's just because Defragging is disk I/O bound not CPU bound, so going multithreaded makes little sense.

[TheWebAtom]

There is also the issue of thread conflicts. Threads are designed not to interact with one another, which means that it's possible for two threads to simultaneously move the same block of data. This would cause data loss or (at the very least) cause the hard drive to become more fragmented.

 

how do you explain all the other multi-threaded programs out there? (multi-threaded gaming, video converting, ect)

These apps perform most of their work on data containing in primary storage; not the hard drive. In the case of games; they utilize multi-threading to allow for background processing without delaying the foreground thread, which would cause choppyness.

[science man]

There is also the issue of thread conflicts. Threads are designed not to interact with one another, which means that it's possible for two threads to simultaneously move the same block of data. This would cause data loss or (at the very least) cause the hard drive to become more fragmented.

 

 

These apps perform most of their work on data containing in primary storage; not the hard drive. In the case of games; they utilize multi-threading to allow for background processing without delaying the foreground thread, which would cause choppyness.

 

What's the difference between primary storage and the hard drive?

[TheWebAtom]

Primary storage refers to memory. Sorry, I'm in essay mode at the moment.

[Super Fast]

@Scienceman: HDD have a read/write head. It performs fastest in sequential reads.

 

Simultaneous reads slow it down because it has to seek multiple locations. It may seem instant, but it is not. It has to physically move back & forward between the locations, so it slows down when it is parallel processing as opposed to sequential.

 

Modern HDD try to alleviate this a bit with an onboard CACHE mem that acts as RAM on the HDD.

 

With Games, the OS typically loads them to RAM & your multi-threaded CPU is able to process them in parallel because RAM doesn't have a read/write head & thus is up to 1,000 times faster than accessing from the HDD.

 

With Defragging, it would be impossible to load the entire HDD to mem for defraggling, and even if it was possible, that would be dangerous because of the possibility of a power outage, etc...

 

* HDD are very similar to CD/DVD access, except CD/DVD read & write to plastic disks via laser, while HDD read & write to metallic disks via magnetic currents.

But the concept is very similar, & HDD are like a very high speed CD/DVD drive.

If you want, try this test to see what the difference would be if you tried to do parallel defraggling with an HDD.

 

Insert a CD with lots of files on it into your CD/DVD reader.

Create an empty folder on your desktop.

Select all files on the CD & copy them to the empty folder.

Time how long it takes.

 

Next, delete the files in this empty folder.

Select 1/3 of the files on the CD & copy them to the folder.

While this is copying, select another 1/3 & select for it to copy these to the folder as well.

Then, select the remaining 1/3 & let it copy also.

Time how long it takes.

 

You will find that the laser is having to switch back & forth to read between the 3 sets, as opposed to the first file copy where everything was sequential.

You will also find that this takes much longer.

 

Hope this helps clear things up!