said by koitsu:As for the Windows 8 Optimiser doing TRIM -- this is completely/entirely superfluous, as the filesystem and I/O abstraction layer already does automatically this upon file deletion and file truncation.
The OS only marks bits as ready for deletion and sends a TRIM command to the SSD. The SSD firmware is responsible for keeping track of the dirty bits and what to do with them. The firmware and garbage collection on different SSDs will do different things with the dirty bits. All the Windows 8 Optimize Drive utility does is explicitly send another TRIM for the entire SSD volume, essentially asking the SSD's firmware to clean the whole thing. In actual use it is probably not needed, but since Optimize Drives is only issuing a command to the SSD, and the SSD decides whether to actually do anything, it shouldn't be a concern.
Windows 7: NTFS will send TRIM hints when files are deleted or moved from those regions; SSDs consume these hints to perform a cleanup in the background called as 'reclaim' that helps them get ready for next writes. The SSD may choose to perform the optimization immediately, store the information for later optimization or throw away the hint completely and not use it for optimization since it does not have time to perform this optimization immediately.
Windows 8: Still does what Windows 7 did above, but the Optimize Drives feature sends a complete set of trim hints for the entire volume again - this is done at idle time and helps to allow for SSDs that were unable to cleanup earlier - a chance to react to these hints and cleanup and optimizer for the best performance.
And most importantly, it does not do a traditional defrag (moving files to optimizer there location for space and performance) on SSDs.
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