The Azure Cosmos DB Gremlin API can be used to store massive graphs with billions of vertices and edges.
Reference:
https://docs.microsoft.com/en-us/azure/cosmos-db/graph-introduction

With Azure Cosmos DB, you can add or remove the regions associated with your account at any time.
Multi-region accounts configured with multiple-write regions will be highly available for both writes and reads.
Regional failovers are instantaneous and don't require any changes from the application.

Reference:
https://docs.microsoft.com/en-us/azure/cosmos-db/high-availability

CONT_SQL3 requires an initial scale of 35000 IOPS.
Ultra SSD Managed Disk Offerings

The following table provides a comparison of ultra solid-state-drives (SSD) (preview), premium SSD, standard SSD, and standard hard disk drives (HDD) for managed disks to help you decide what to use.

References:
https://docs.microsoft.com/en-us/azure/virtual-machines/windows/disks-types