Approximate RAID rebuild times

It depends on several factors including drive model, capacity, and whether it is an HDD or SSD. An SSD RAID will rebuild at a rate of about 1 hour per Terabyte. For example, a RAID that consists of 2 x 4TB SSDs will rebuild in about 4 hours. An HDD RAID will rebuild at a rate of about 1.5 to 2.5 hours per Terabyte. For example, a RAID that consists of 2 x 8TB HDDs will rebuild in about 12 to 20 hours.