Recommended free space for SSD-drives: Leave it completely unformatted or just unfilled with data

hard drivepartitioningspeedssd

Several topics in this board point out the recommendation about leaving 10 % – 25 % of free space when using SSD-drives.

The central question now is:

  • Does this 25 % recommendation refer to a completely unformatted blank rest space on the disk? (= unformatted raw partition)

    or

  • Is it okay to format the whole disk with a filesystem in complete disk size, but later just pay attention to avoid filling up the filesystem with data completely (= leaving 25 % empty space inside the formated partition)?

Best Answer

You don't operate directly on the flash layer of the drive, you work on a layer above the wear leveller so the two cases you mention are functionally the same.

If it is a brand new drive and you know for certain that it has never been used then the two cases will be identical.

If you have used the drive fully partitioned then you cannot guarantee where the operating system will have allocated on the drive, in this case continuing to use a full partition would be better as the operating system can issue TRIM commands to clear the empty space.

TRIM commands specifically tell the wear leveller what blocks have been made empty and can help the drive make intelligent choices about where and what to move so having the operating system make it absolutely clear what blocks can be erased without consequence could make things better in the long run, especially if you allocated and used the space and then just deleted the partition.

I've posted more on the Flash Transition Layer over here.

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