Showing posts from July, 2017

vSAN RAID Levels and Fault Domains

One of my customers is considering implementing vSAN, so I've been researching it quite a bit lately.  The interactions of vSAN RAID levels (for all-flash configurations) and Fault Domains is fairly complex, so I figured that I should post some notes about what I've learned here.

First, the concept of RAID is a little different in vSAN than it is in a traditional array.  Traditionally, RAID specifies the algorithm used to spread data (or parity data) across a set of disks.  For example, RAID 5 specifies that data will be striped across all of the disks in a set, with a single disk's capacity used for parity.  This means that a 3 disk RAID 5 set will store data on 66% of its disks' capacity.  A 5 disk RAID 5 set will store data on 80% of its disks' capacity.

vSAN treats RAID differently.  There are 3 different RAID types that vSAN supports: RAID 1, 5 and 6.  Like in a traditional array, these RAID levels describe the data redundancy algorithm used, but the members a…