Seen in e-mail today:
From: Mark Kirkwood
There are a number of considerations (disclaimer we run Ceph block and Swift object storage):
Purely on a level of simplicity, Swift is easier to set up.
However, if you are already using Ceph for block storage then it makes sense to keep using it for object too (since you are likely to be expert at Ceph at this point).
On the other hand, if you have multiple Ceph clusters and want a geo replicated object storage solution, then doing this with Swift is much easier than with Ceph (geo replicated RGW still looks to be real complex to set up - a long page of archane commands).
Finally (this is my 'big deal point'). I'd like my block and object storage to be completely independent - suppose a situation nukes my block storage (Ceph) - if my object storage is Swift then people's backups etc are still viable and when the Ceph cluster is rebuilt we can restore and continue. On the other hand If your object storage is Ceph too then....
Mark's perspective is largely founded in the fault tolerance and administrative overhead. However, let's a look at "keep using [Ceph] for object too".
Indeed the integration of block, POSIX, and object storage is Ceph's strength, although I should note for the record that Ceph has a large gap: all 3 APIs live in separate namespaces. So, do not expect to be able to copy a disk snapshot through CephFS or RGW. Objects in each namespace are completely invisible to two others, and the only uniform access layer is RADOS. This is why, for instance, RGW-over-NFS exists. That's right, not CephFS, but NFS. You can mount RGW.
All attempts at this sort of integration that I know in Swift always start with a uniform access first. It the opposite of Ceph in a way. Because of that, these integrations typically access from the edge inside, like making a pool that a daemon fills/spills with Swift, and mounting that. SwiftStacks's ProxyFS is a little more native to Swift, but it starts off with a shared namespace too.
Previously: Swift is faster than any competitor, says an emploee of SwiftStack.