Question A Real Mystery


Junior Member
Jun 13, 2023
This is a head-scratcher.


I am getting ready to start building up a new computer and will be moving four physical hard drives over from the old PC to the new PC. These hard drives contain photos and back-ups of the photos and data files (documents, music, etc.). Basically 2 HDDs (4TB each, X: and Y:) that hold different photo catalogues, a 10 TB HDD that holds back-ups of the 2x4TB drives, and another 4TB HDD that backs up other documents, music, etc. plus program files (P: and Q:). On my existing PC, in addition to these HDDs I have 3 SSDs for the O/S, documents and program files (1TB, 2TB and 1TB respectively C:, D: and E:).

Still trying to source out a new case for the new build looking for something that can hold at least 4 3.5 inch HDDs. In the present day that limits my choices. I have an old MediaSonic 4 drive external e-sata/USB Raid Enclosure so I think to myself, compare speeds of the HDDs currently in my existing build, drop the drives into the MediaSonic and compare speeds and see if comparable or not. Just to see if maybe I don't need a case with room for the 4 HDDs. So I start out physically pulling out all 4 HDDs out of my old PC and just putting the P: and Q: drives in the external enclosure to test speeds (not good BTW).


Here is the part that is weird. My two photo drives (X: and Y:) are sitting on my desk not connected to anything. Windows Explorer shows 4 drives, C:, D:, E: and Y: (??? (Y: is not physically connected to the PC)). Disk Management also shows 4 drives, and the properties of the Y; drive indicate a physical HDD (WDC WD40EFRX-68WT0N0). I can access photographic files with Adobe Lightroom from this Y: drive. But my case is wide open, and there are only the three SSDs. Nothing else.

Anyone have any idea what is going on???

I will add that in the past, Windows Explorer did show two Y: Drives which I always attributed to some odd glitch and so I ignored it.

Additional Info:

I benchmarked the Y: drive with CrystalDiskMark before removing it and had read/write speeds of 146.2/137.0 MB/s. I just reran this with the mystery Y:, and it only reported Read speeds in the 22,500 MB/s range. Did I somehow set up a copy of my Y: drive onto a RAM-disk? No idea how I managed that if I did so. I would have thought doing so would have required a pretty comprehensive setup process (that I would have noticed) rather than possibly an accidental keystroke somewhere.


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Golden Member
Mar 21, 2007
Not sure what version of Lightroom you are using or if they have changed things since earlier versions (I'm still using version 3.4), but as you probably know the Lightroom library is stored on the drive of your choosing, in your case likely the C drive if you were able to open it. Image previews are also stored on this drive. So it's possible to view the library without the photo drive attached. Did you try editing any of the images or just view them?

I have no idea why the drive would be accessible in CDM with it disconnected though. What does disk management show for drive Y with it disconnected?

Tech Junky

Diamond Member
Jan 27, 2022
I think it's mostly a glitch since no drive can hit 22GB/s on its own nor will you have 4TB of RAM.

It seems more like you might have somehow mirrored the HDD to one of the NVME drives and somehow enabled some caching option in Windows or maybe a shadow copy to the NVME.

Windows doesn't like 2 x the same logical name for drives so, that feels more like a shadow copy situation or some random coincidence.

To get the speed CDM is reporting though you'd need a Gen 5 NVME or bundle a few together in Raid 0 and your listing for drives doesn't add up to that speed / capacity.
Jul 27, 2020
It's not a mystery at all. You don't get a drive suddenly out of nowhere. At some point, you (or the person who configured your system), must have installed some software or assigned a drive letter to a folder (like a mount in Linux).

Another thing. The really high speed (and the fact that the test is using only 1GB test file) leads me to believe that you are using some sort of caching software, either paid or something free that came with one of your SSDs. Take a look in task manager and see if you can find anything unusual. Or look in the system tray. This could be Primocache or some option activated in Samsung Magician SSD dashboard.

Go to Add/Remove Program and look at the list of installed applications very closely.
Jul 27, 2020
The issue with a cache setup is that your PC must be connected to a UPS to avoid data loss, especially if your data is critical to your livelihood.