Hi Al and all others,

quite a while ago the differences of SSD and traditional HD were discussed under the aspect of minimum free sectors needed to guarantee speedy access to the directory/file system.

The view grown from expirience on HD was that at least 5%, better 10% to 15% of a logical volume should be left free or many operations might take longer. Also defragging at regular times would speed up disk acces of defragged files and creation of new ones, as free space is continuous.

With SSD the need to defrag not only evaporated, but defragging SSD is a no-no as it incurs unneccassary writes, shortening the life span of SSD. The controller of the SSD will map dying/dead SSD cell sectors to free/unused area with no big changes to operating speed.

But what is unused/free in SSD terms ? There is an area marked as unreachable, where "reserve" sectors are kept. I believe in some SSD offerings you can widen or shorten that area. Then you have partion(s) on the raw physical device, which used to be 1-3 primary partions and an extended one where more logical partitions could be placed. Now GPT partition is probably standard on pre-installed machines. On all schemes often there are some areas left either "free" or dedicated to reinstall/set-back options.

On windows tyically each partition becomes a lettered drive (ignoring RAID and chained resources on purpose) with unused/free sectors again.
Going one step further, you can create .VHD, .vdi or .VHDx on your partitions files you can mount as drives, each having unused/free space as well.

So: which "free" sectors are counted as free to guarantee best possible device speed on SSD ?

Head scratching...

thomas