MacBook Air upgrade with WD SN750, but write Speed is unstable

[Chiradeep]

I have upgraded MacBook Air 2017 SSD with WD SN750 NVME M.2. 250GB with adapter. After installing Mac OS Big Sur, the Black Magic write speed comes up to 1282 MB/s and goes down to 629MB/s, (write Speed Unstable), TRIM is enable. Read speed is good 1298MB/s . Kinldy help me out to fix the problem !

 

[tps3443]

I have upgraded MacBook Air 2017 SSD with WD SN750 NVME M.2. 250GB with adapter. After installing Mac OS Big Sur, the Black Magic write speed comes up to 1282 MB/s and goes down to 629MB/s, (write Speed Unstable), TRIM is enable. Read speed is good 1298MB/s . Kinldy help me out to fix the problem !

I imagine the write speed is great until the SSD's cache fills up, if you are transferring files that are larger, then it will slowly deteriorate in write speed. This is normal for most SSD's Especially a 250GB NVME SSD. It will have a drastically smaller cache of probably 512MB or possibly even less than that.

If you are writing at sustained speed of 600MBPS while transferring larger files, you're doing pretty good.

The manufacturers list the specs base on so many variables.

Your performance looks good to me. This is a 256GB NVME that has a write speed of 1,600MB per second. Now, that is using like a small file more than likely. When you start transferring larger files, it starts out fast, that cache fills up, and the write speeds just drops down.