Here is a list of the different kinds of "private RAID groups" that are created as part of a storage pool "behind the scenes" depending on the number of similar drives within the pool".
<div><strong>RAID 5</strong></div>
<div>
<ul>
	<li>2+1 (3 disks)</li>
	<li>3+1 (4 disks)</li>
	<li>4+1 (5 disks) ** RECOMMENDED</li>
	<li>5+1 (6 disks)</li>
	<li>6+1 (7 disks)</li>
</ul>
<div><strong>RAID 6</strong></div>
<div>
<ul>
	<li>2+2 (4 disks)</li>
	<li>4+2 (6 disks)</li>
	<li>6+2 (8 disks) ** RECOMMENDED</li>
	<li>8+2 (10 disks)</li>
</ul>
<div><strong>RAID 1/0</strong></div>
<div>
<ul>
	<li>1+1 (2 disks)</li>
	<li>2+2 (4 disks)</li>
	<li>3+3 (6 disks)</li>
	<li>4+4 (8 disks) ** RECOMMENDED</li>
</ul>
</div>
</div>
</div>