Slow "optimizing in the background"

Hi all,

Just want to ask if this is normal. 1st time creating a new volume and storage pool in years. I put it in 3x 8tb in my DS1517+ and created an SHR volume. It says here optimizing in the background time left 12 days plus and this has been going on for 3 days now. Is this normal? I don't remember rebuilding RAID or creating a new pool taking this long.

Thanks guys!