Overview
Over the course of a few months I purchased two of the same SSD from different stores (both 960GB SandDisk SSD PLUS, same firmware(Z33110RL) - just waited for them to be on sale) with the intention of combining them in RAID0.
When the second drive arrived, I benchmarked both to make sure everything was working.
For convenience, I used a drivebay (like in the image above) on a SATA port configured for hot swapping in the BIOS to test the two drives using CrystalDiskMark. I used the same sata port, simply swapping one for the other.
I noticed that one of the drives (the one I had just purchased, and so had not used yet) was performing drastically worse than the other, despite being on the same motherboard(GA-Z97M-D3H), on the same SATA connection, and the same model(960GB SandDisk SSD PLUS) with the same firmware(Z33110RL).
Different Transfer Mode
I tried forcing Trim, reformatting again, copying some files to it, etc. but the results were consistent, and I tried swapping the drives back and forth several times; The results never changed, and the new drive was consistently about 1/4 of the speed of the other one on Sequential tests.
Checking CrystalDiskInfo to see if there were any discrepencies, I noticed that the slow drive was showing its Transfer Mode as SATA/150 | SATA/600, meaning that it was using SATA/150 but supported SATA/600, while the other drive was showing SATA/600 | SATA/600.
The slow drive:
The fast drive:
Swapping the two drives will consistently yield this behaviour, the newer one (serial number ending in 193) is always using SATA/150, while the other one (serial number ending in 876) is always using SATA/600.
Question
What would cause this behavior? What determines the selected 'Transfer Mode' for the drive?
The drives are -identical-, both formatted to NTFS, and are being tested on the exact same motherboard/port/etc.
I have used this hot-swap bay with dozens of drives before, and none have ever acted up like this.
