Hi All,
I need information about availability zones in nova. I tried googling but cant find enough information. My questions are ,
1. Why is it that we have two concepts of aggregates and AZs ? Is one not enough ? Like exposing aggregates and creating flavors with extra specs to match ? Why do we need AZs also ?
AZ isn't for picking the right type of host. It's for picking hosts that are distributed. Maybe you want a host with local disk. Great, you use aggregates / flavor specs for that. But what if you want instances for a myself cluster or setting to each be in different racks? Then you need AZs.
2. Why is it that one node should only be a part of one AZ but not two ? whereas in the case of aggregates, it can overlap ?
Overlapping failure domains would be pretty confusing and pointless.
3. Also why cant we expose only aggregates like AZs but block the compute member list to the users ? Doing this way will serve the purpose of AZ as well ? Why we dont want to expose aggregates as AZs ?
They're mutually exclusive concepts.