Does the more filled a mSSD / SSD get, the slower it gets ?

I know it's a stupid question but I honestly don't know .

Basically if I use an mSata as a OS drive and it fills 54gb out of 60gb will it be slower then say if it gets filled lower like 26gb out of 60gb ?

 

From what I remember when I was researching SSD for my purchase, the answer to this is yes. At least the writing speed will go down because it will have some difficulties finding empty cells.
Overprovisioning help to mitigate this problem though.
I'm guessing the read speed is unaffected or at least not as severe as write speed reduction

 

It also depends on the controller too and how it deals with filled cells. I can tell you my Vertex 2 80 GB and my Agility 2 60 GB were very slow when it was like 80% full. I've never had an issue with Intel/Samsung SSDs (320 series, G2/G1, PM810, PM800, 830, 840).

 

Well the one I'm looking at MyDigitalSSD BP4 1.8" mSATA SSD's: 240GB $160, 120GB $90 & More + Free Shipping - Amazon Deals, Coupons and Promos

Has a S8 / Phison controller ? I have no idea what that means .

Edit : Woops nevermind, the price jumped .

 

Yeah, Sometimes theres only 11 GB left on my 256 GB Samsung 830 (which is better than most I beleive)
but I overprovision it around 20% as they suggested and the speed stays excellent.

You should set up notification on slickdeals, that's how I got better price on SSD

 

As mentioned it depends on controller and partly the nand configuration . the main metrics affected are random write and sequential write performance. Power efficient controllers, like the phison coupled with less performance oriented nand arrays (e.g quad channel vs 8 channel), rely much more on striping data across multiple nand packages in order to achieve high write performance thus are more sensitive to losing performance as it fills up compared to more powerful controllers like the Barefoot 3 in the ocz vector or enterprise optimised solutions like the LAMD in Neutron drivers.
That being said, all ssds suffer some degree of performance degradation as it is filled, the difference between them is the magnitude and tradeoffs that the various vendors make. Decreased sensitivity almost always comes at a cost of peak burst performance and/or consistency . E. G. The Samsung 840 pro is an 8 channel design that is purely optimised for peak performance, hence it is extremely sensitive to losses in sustained performance and consistency when filled up.