Question NVME Drive Speed slowdown as they fill...


Platinum Member
Nov 18, 1999
I've got the following drive and was curious about how it will slow down as it fills near its 2TB size:

SK hynix Platinum P41 2TB PCIe NVMe Gen4 M.2 2280 Internal SSD l Up to 7,000MB/S l Compact M.2 SSD Form Factor SSD - Internal Solid State Drive with 176-Layer NAND Flash

In the old days of platter HDDs, my recollection is that speed exponentially decreased with each MB closer to fill capacity. SSDs behave similarly though the slow was maybe less (anyone know a good rule of thumb here?).

And for NVME Gen 4... Is there any basic rule of thumb that describes the slowdown as the drive fills? i.e. Advertised drive speed for first 95% fill, then drops 15% in the last 5%... Or something along those lines...

Tech Junky

Platinum Member
Jan 27, 2022
I don't think there's a rule of thumb on when a drive slows down based on remaining capacity but, I try to keep things slimmed down to get the best performance.

Benchmarks though will show a decrease in speed beyond 70%. The more time it takes to find free spots for data is what slows it down.

I mean with an NVME you'll still be 10X faster than a HDD anyway and if it slows down a bit you won't notice anyway. The only time that 7GB/s transfer speed matters is when you boot the PC and when you launch a game. Otherwise it's idle.
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Zor Prime

Senior member
Nov 7, 1999
I don't have an answer to the question but I use this very drive you mentioned and it's fast. I've filled it up to around 60% capacity and I've noticed no performance hiccups, but even if there were performance degradation it's still so fast I'd probably not notice outside of a benchmark graph.

When I transfer large amounts of data from it to a Gen3 Mushkin Pilot-E I see real world transfers peak over 2GB/sec at times. That's just nuts.
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Diamond Member
Jul 27, 2020
The main problem you might face with drive filling up is that your NAND will degrade faster because the wear leveling algorithm of the firmware needs free flash cell blocks. The less blocks there are, the more writing needs to be done to ensure that all the blocks are used in a balanced way to avoid some cells reaching end of life before the others.

If you fill up to like 98 or 99% of available space, spare flash cells may then need to be used which are normally reserved for emergency cases of sudden flash cell failure. So this will reduce the overall life of the drive. Still, I don't think you should face too many problems because something like a game drive would be more read intensive than write intensive.

Also, I don't think reading will slow down much. Usually only the writing speed of the drive may be affected as the drive fills up.

One word about CrystalDiskMark. It can do a lot of writing. Last time I ran it with 4GB file size, it ended up writing 40GB to the drive. Something to keep in mind if you are concerned about your drive's endurance and remaining life.
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Diamond Member
Jun 8, 2005
There is no solid rule of thumb really. Consumer drives that rely on SLC caching will already have widely varying performance profiles. Not only do they differ in SLC cache capacity from drive to drive, but also depending on the capacity of the same drive type you buy. Even if you buy the same capacity NVMe drive, 2 different companies drives could have different SLC caching capacities at different physical capacity points. On top of all that, without Powerloss Protection (Most consumer drives), there is quite a bit of variation in drive performance as each manufacturer tries to squeeze out burst performance while providing at least a little resilience in flushing transactions. Enterprise drives are generally much more consistent with Powerloss Protection, as well as generally lacking the SLC caching feature (for the most part).

One rule that tends to work in general is that 75% to 80% drive usage as an upper limit keeps performance near out of box levels. However, that does not apply to SLC caching because most drive manufacturers rapidly begin decreasing the amount of SLC cache available as the drive starts filling with data. But most enterprise applications will stick with 75 to 80% capacity usage.
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