Openstack: how object storage to be used by apps running on VM?

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http://serverfault.com – I'm new to openstack, now reading some documentation. I have question about the object storage. Could the swift object storage be used by apps running on virtual machine? I guess the answer should be YES. If so, do apps also use the Openstack HTTP based API to operate the storage? I'm afraid the performance issue. (HowTos)