Volume 2 is at 95% even though I have 4.11 TB available

On my MyCloud EX4 I have 4, 4TB HDs installed running a RAID1 config. I recently added the last two HDs and noticed that the total capacity of the storage increased. In the screenshot, there’s 4.11 TB available, however I am getting the red LED light as it states “Volume 2 is over 95%”.

How do I fix this so that the total of all volumes is the full 8TB?

So you have two RAID 1 configure for all those 4 hard drives? If seems like one of your RAID1 volume is fill up. From the screen shoot you have use a total of about 3.3TB.
If you have two RAID1 which is 4TB each, then you total capacity would be around 8TB.
Take 8TB subtract 3.3TB, which give you about 4.1TB left. Does that make any sense to you?

Hi,

You could refer to the following link: https://support-en.wd.com/app/answers/detail/a_id/24755

Given you have 4 disks, RAID 5 will provide fault tolerance with less overhead

larger NAS units use RAID 6 which can tolerate two disks failing