Replacing a hard drive

As long as the replacement drive is on the Hardware Compatibility List (HCL) and is equal to or larger than the smallest drive in the array. You can mix brands, models and even 5400/5900/7200 RPM drives.

Note: Western Digital does not recommend their Green Label drives in RAID configurations, but are on the HCL. A better choice, although a bit more expensive is their Red Label series which are expressly designed for RAID use. Enterprise drives of all manufacturers which are far more expensive are also designed for RAID use.

I have run arrays with 2x1TB Seagate 7200RPM drives and 2x3TB Hitachi 5400RPM drives without any problems for the past year. Prior to that for about a year, I ran an NV+ with 4 drives of 2 different manufacturers, 2 different models and 2 different sizes. Of the four drives only two were the same make and model.

Mixing drive models is fine (and some people think it actually is a good idea).

Though I am running some of the WD Green drives, when the time comes to replace them I will go with the Red label.