VSAN group fail


i need to know one thing regarding vSAN,

i have 3 hosts and each host have 2 groups ,group A and group B.

if host 1's group A's SSD fail , .SSD fail group A (degraded) am i right..then what will happen next..

vSAN where will write groups A's objects..?

1 Reply
VMware Employee
VMware Employee


Assuming your VMs are all using Default vSAN Storage Policy (which has FTT=1 - Failures To Tolerate=1) they will have 2 data+1 witness component per Object (e.g. a vmdk, vswp or namespace). The components that resided on the failed disk-group (group A here) will be recreated on the other available disk-group(s) on the host (or on another host if 4-host or larger cluster), so group B here as it is the only available.

However it will only be able to rebuild these components on group B provided there is enough space, so if the disk-groups are >50% full it won't be able to rebuild all of these. Thus issues such as failed disk-groups when using small clusters with few disk-groups per host should be remediated asap (as it should be on any cluster but it won't be as much of an issue on a 4+node cluster or hosts with more DGs).