The option whether to use vhost vs path style is the application's choice, e.g. whether it uses

http://bucket.server.example.com/objectname

or

http://server.example.com/bucket/objectname

Thanks. Is path style addressing the default? The questions are related to ECS configuration and how or when you'd configure a base URL. The help ECS states to create a base URL when using virtual host style addressing. I'm wondering if creating a base URL is necessary if an application uses path style addressing.

I don't think path style is necessarily the default, but we typically recommend its usage over vhost buckets because it's overall simpler to implement.  For example, if you're trying to use vhost addressing and also want https, the certificate must be wildcard.  You do not need to configure a base URL in ECS if the client/application is using path style addressing.

What happen if the ECS is used by cloudpool and cloudtier?  Cloudpool will use virtual host style addressing but cloudtier can it use path style.