I just lost 44 GB of data that I downloaded in the past two hours. My PC started to get laggy and it got stuck so I just shut it down believing that all will be well since the data has already been written to disk…
This is incorrect too. The OS buffers writes to drives for performance, a portion is kept in memory and flushed to disk when possible. A sudden power loss can easily result in a partial write.
That said a drive failure is also possible.
The filesystems journal will be the source of truth.
The buffer is flushed every 6 seconds. OP was pulling down 44GB/7200sec = 6MB/s. OP would have only lost 36MB to disk caching.
If it was a single 44GB file and OP turned off less than 6 seconds after it finished, then it could have been caching. But that’s very unlikely.
44 GB over two hours, though? If it were the last couple GBs in the last maybe 10 ten minutes, but unless the OP is running a PC from 2002, the data should have already moved from RAM to disk in that time.
But yeah, the filesystem journal will explain what happened there.