Will SSD read/write performance decrease for a partition that is low on space if the drive itself has ample free space?

  • 1
    Unless dealing with thousands of small files, it should not slow down at all.
    – John
    Feb 3 at 19:46
  • @FrankThomas I think what you have written may be misinterpreted - the partitioning is a software abstraction - the ssd sees itself as a block device and will move data arround at the block level and will reallocate blocks regardless of how full a partition is. Also, as a disk fills up there is less space to wear level and an SSD may indeed slow down.
    – davidgo
    Feb 3 at 23:58

2 Answers 2


No, it can't.

The firmware of the SSD knows nothing about partitions. It only knows about and manages sectors. Partitions are handled by the operating system (and the BIOS).

If your disk is slowing down, check its SMART attributes to verify its health. If you don't already have a product for it, use Speccy, which will also analyze the variables and mark each one as Good or not.

Include a screenshot of the SMART attributes in your post, if you want us to have a look.


There are circumstances that can slow down a SSD besides availability of erased pages that do not by definition mean any kind of damage or malfunctioning. For example 'static' data at some point will require more effort and time to be read even though modern SSD's patrol and refresh such data upon reaching a certain threshold.

But since there's no static relation between LBA sectors and physical NAND memory, the SSD does not care about free space within the partition, if it even had any concept of it, which it has not. While we regard the partition a linear array of LBA sectors it is actually spread over the SSD. As long as the SSD 'remembers' where each of the sectors are, we (the operating system) can treat the partition as an area on a drive.

In other words, assume 100 GB partition (1) and a 140 GB partition (2) on a 240 GB SSD. Then assume partition (1) has 15 % free space while partition (2) has 50% free space. We also assume the SSD is aware of the sectors that aren't in use as the operating system TRIMs deleted sectors so it can pro-actively erase those.

This means overall SSD has 35% space available to store new data which is a very healthy amount, even for partition (1) which itself has only 15% free space available from the perspective of the file system.

Then we also need to consider there is likely more 'free space' due to overprovisioning by the SSD firmware: Even if you'd fill the SSD up 100% it needs some working space, somewhat similar to a slider puzzle. BTW, this does not mean I encourage anyone to fill up the SSD fully. The more 'free space' the smoother the SSD will function as it will make wear leveling easier and will help the SSD have an amount of erased and ready to go blocks available.

enter image description here

Of course there is the 'normal' wear that will eventually degrade any SSD.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.