Sorry, I promised I&#x27;d let us agree to disagree, and I will after this, but I just can&#x27;t help myself on this one point:<p>&gt; This is again wrong. A 3 disk RAID1 has the size of 1 disk and a 3 disk RAID5 has the size of 2 disks so they&#x27;re not the same. To make it comparable you need to make the array RAID6 at which point you have the same space and redundancy. You&#x27;d still do a RAID1 though as for the 1 disk size case there is no added benefit of parity.<p>Pardon, but <i>what</i>?<p>Think about this for a second.<p>For one, now you&#x27;re moving the goalpost by shifting gears to disk capacity alone (which, as I&#x27;ve mentioned repeatedly, is a non-factor if you&#x27;re considering anything mirror-based).  <i>With the same number of disks</i>, mirroring always beats parity in a RAID.  There&#x27;s no getting around that.<p>Don&#x27;t believe me?  Take those four disks (you need four at minimum) in your RAID6.  Your array can survive two disk failures.  Now I build a RAID1 with four disks.  Mine can survive three disk failures.  Yes, there&#x27;s a capacity hit, but it&#x27;s been <i>repeatedly</i> established that it&#x27;s not <i>capacity</i> that matters.<p>This still holds true when comparing a three-disk RAID5 and a three-disk RAID1.  This still holds true when comparing <i>any</i> n-disk n-1-parity-block array with <i>any</i> n-disk RAID1 with the same value of n.<p>Your points are much more valid when they&#x27;re targeted at RAID10 instead of the concept of mirroring in general.