Hard disk slowdown problem

The situation is like this. Normally, the continuous writing speed of large files is about 150, or even higher. Suddenly, this situation occurred. When testing the sequential speed of large files with software, the reading speed is normal, but the writing speed suddenly becomes more than 60. Drag a file of dozens of GB in, the speed is about 180 at the beginning, and after testing a few GB, the speed drops to more than 7 in a few seconds, which is the same as the test (a bit like the curve when the SLC cache of the solid-state drive is used up). If you copy this file and then copy the next large file, the phenomenon is similar. So I tried to move the data out, delete the partition and re-partition it. At this time, the copy and test data are normal. Then shut down and leave it overnight, test and copy again, and the writing speed becomes slow again. The reading speed has been normal. Tested in the PE system, the same phenomenon. The bad sector test passed, no bad sectors. Smart data is normal. Obviously, it doesn't seem like a disk failure in some areas, otherwise it is impossible that the first few GB of data speed is normal every time, and it should not be the cache that causes the first few GB to be fast. The cache is only 64M. It doesn't seem like a firmware problem. After deleting the partition and repartitioning it, it was normal no matter how I tested it. But it became wrong again after I shut it down and left it overnight.

Please help analyze the cause.

Although disabling the write cache can solve this problem, it will cause the hard disk performance to decline. The write cache is to use a part of the memory as a cache. After disabling it, it will be written directly to the hard disk, and the performance will definitely be affected.

But I saw someone on reddit report that turning off the write cache still caused frequent crashes? The reason is unknown, so if there is no download stuck io, it is recommended not to do this operation.

The cause of this problem is not clear at present. Firmware problem? The Windows hard disk driver? No one has found the specific cause yet. However

It seems that this "bug" has existed for quite a long time, but there is no good solution so far.