WD Black SSHD transfer speed very low and erratic as external disk


I have WD500M22K Black SSHD with 16GB cache, got it in my yoga 2 11 tablet. I upgraded yoga with SSD and planed to use WD Black SSHD as my external storage drive. I bought external SATA case, put my WD in it and connected it trough my 3.0 USB port on yoga, formated drive and started using it on Win10 Home. And here goes disappointment. When i copy files (for testing purpose i used 10 gb file, but even when i used smaller files behavior is almost the same) from internal SSD to external WD speed of the transfer is very erratic, but most of the time it is 10 Mb/s…!!! Sometimes on transfer start disk reaches speeds of 130 Mb/s but that lasts around 10 seconds and then drops to 10 Mb/s.

I tried with two external SATA cases from different manufacturers to exclude case problem but results are the same. Interestingly when i benchmark it trough christal disk mark benchmark with 4GB file it says that speed is 130 MB/s…!!! But i can’t obtain this speed in real use when copying files. I checked disk with WinDlg WD diagnostic tool and everything is ok. And USB port is for sure 3.0 as when i connect my Passport external disk to it speeds on transfer from internal SSD are 50-60 Mb/s. So, my question is can i use this disk as external disk with full speed on transfers (100+ Mb/s) or that speed can only be obtained when disk is system disk?

Can anyone help with this isue, thanks…

Hi there,

I have not tried this, however i would like to know what happens if you test a different internal drive on the SATA case you would get the same results, lets se eif anothe ruser can share some information or tips on this matter.