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I'm not sure if solid state drives need defragmentation. Can anyone tell me if this requirement goes away with the new technology?

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up vote 6 down vote accepted

No, never. Defragmentation is helpful on spinning platter-based drives, if the filesystem doesn't handle it (which HFS+ generally does, on a Mac), because it takes time for the disk to spin around to the right spot, which has to happen more often if one chunk of data is split between several locations. See Access Time.

A solid state drive has no moving parts, so there's no mechanical delay. Reading a section of data takes approximately the same amount of time no matter where it's located in the flash.

Defragmenting a solid state drive is actually harmful because it forces the drive to move data around for no good reason, and flash chips have a limit on how many times they can rewrite a section.

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Defragmenting an SSD is actually technically not possible since the wear-weaving will distribute any freshly written blocks across the chips anyway. Allocation blocks (like sektors on a spinning harddrive) aren't physically contiguous in flash memory. – MacLemon Nov 21 '12 at 22:29

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