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Mokubai · 01-31-07, 11:50 AM

I'm really not sure that "defragging" a memory card will work, the CF and SD memory cards incorporate controllers that use wear-levelling which means that when a memory block gets written to and then subsequently marked as blank instead of using that same block for that part of the disk a new one gets allocated to take its place. The FAT file system that is seen by the device using the memory card is simply a presentation of how the card *could* work to the operating system but the physical representation could be phenomenally different in terms of actual layout.

So, due to wear levelling, you could have a file that the FAT file system shows is completely contiguous but in the physical media is as fragmented as a file can possibly be. The reason that FAT32 and / or FAT backup make a difference is because you are making the FAT file system more representative of the physical media and so using it more efficiently.

This is my interpretation of the FAT + wear-levelling interaction and *could* be wrong but I have spent some time trying to find out just how this works so I do have a reasonable idea of what is going on. Feel free to correct me if you know better though, I am wanting to understand this better.

01-31-07, 11:50 AM	#12 (permalink)
Mokubai Aximsite All Star Join Date: Dec 2005 Location: UK Posts: 833 Device: HTC Touch Pro 2 Carrier: Vodafone UK Thanked 0 Times in 0 Posts	I'm really not sure that "defragging" a memory card will work, the CF and SD memory cards incorporate controllers that use wear-levelling which means that when a memory block gets written to and then subsequently marked as blank instead of using that same block for that part of the disk a new one gets allocated to take its place. The FAT file system that is seen by the device using the memory card is simply a presentation of how the card could work to the operating system but the physical representation could be phenomenally different in terms of actual layout. So, due to wear levelling, you could have a file that the FAT file system shows is completely contiguous but in the physical media is as fragmented as a file can possibly be. The reason that FAT32 and / or FAT backup make a difference is because you are making the FAT file system more representative of the physical media and so using it more efficiently. This is my interpretation of the FAT + wear-levelling interaction and could be wrong but I have spent some time trying to find out just how this works so I do have a reasonable idea of what is going on. Feel free to correct me if you know better though, I am wanting to understand this better. __________________ pencil and paper: n.An archaic information storage and transmission device that works by depositing smears of graphite on bleached wood pulp. More recent developments in paper-based technology include improved ‘write-once’ update devices which use tiny rolling heads similar to mouse balls to deposit colored pigment.