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Fedora never has a place in the server space in the first place, CentOS is the Fedora derivative that has. Debian is losing ground and CentOS is eroding some corner of SLES while SLES is doing well in area where NetWare was strong. eDirectory is also doing good for SUSE, so is interoperability. But SLES as a general purpose server OS is losing, it's just bad.
Ubuntu is gaining some ground in clustered cloud server, but not on the general server market.
That's my own number, I work with those OS.