Why do we need both mirror-vault and vault of snapmirror types?

[heightsnj]

SnapMirror could have mirror-vault and vault-type, in addition to mirror-async type. 

If I want need to have both vault and mirror type, I just need to have mirror-vault, is there any reason, I want to separate mirror and vault?

Thanks!

[Sergey_Osipov]

vault is a long-term backup solution.

you replicate specified snapshots defined by label and store them on destination by specific retention times.

mirror is a DR(disaster recovery) solution to be able to serve data from a destination side in case something happens with primary site.

Basically mirror can be either replicating everything from the source (AFS+all the snapshots) or AFS(active file system) only. 

mirror-vault is a mixed solution which provides you advantages of the both solutions simultaneously

https://kb.netapp.com/Advice_and_Troubleshooting/Data_Protection_and_Security/SnapMirror/What_are_the_SnapMirror_policy_types_and_what_do_they_mean%3F