The speed of my disk greatly decreased .

The speed of my sdssdx120gg25 disk greatly decreased .
I Motherboard MSI Z77-GD65

AHCI - enable

Windows 7 x64 SP1
This computer disk works a year and worked in the previous half year .
Earlier in the test Windows 7.9 units for the drive on the old and new computer.
But now the rate has dropped substantially , slow .
What is unclear delay.
TRIM function tested - works .
The disc is full is not much , even specially cut a piece of 20 GB and leave it unformatted .
Big Air - this is the current computer on test .
In PASSMARK8  #4840(my old PC) worth the same disc - years ago.

and #4834 (my now PC whith HDD on test)
I do not understand how to restore the disk , please help me.

pic 1

pic 2

pic 3

try secure erasing the SSD and reinstall. That should restore the original speed. 

to drlucy:

Thanks for the advice. But the question is - why it happened and how to avoid a recurrence of this problem?
I do not want to reinstall the OS every year.

Sorry to say, none of the test results in your pictures show any big change in that SSD. The WEI score is 5.9 in all the pictures, the AS SSD results are almost identical and fine for that SSD, and the Passmark results look very good.

Don’t forget that the WEI disk score is based on all the disks in a PC, the more disks in the PC, the more one or more slow ones (HDDs) will reduce the score.

_ Passmark results look very good. _

It amazes me your statement. Compare what the result was this drive and a half years ago(#4840) and now (BigSilver) 

Speed slipped on all counts.

And now look at the AS SSD write speed and Acc. Time :robotsurprised:

That might be due to wear and tear. I wouldn’t give much attention on it since that’s normal. Just my opinion though.