Revert "Revert "fix(server): only set NOCOW for log file""

This reverts commit 9540575690.

Conflicts:
	etcd/etcd.go

server/peer_server.go

@@ -19,6 +19,7 @@ import (
 	etcdErr "github.com/coreos/etcd/error"
 	"github.com/coreos/etcd/log"
 	"github.com/coreos/etcd/metrics"
+	"github.com/coreos/etcd/pkg/btrfs"
 	"github.com/coreos/etcd/store"
 )
 
@@ -291,6 +292,11 @@ func (s *PeerServer) Start(snapshot bool, discoverURL string, peers []string) er
 
 	s.raftServer.Init()
 
+	// Set NOCOW for data directory in btrfs
+	if btrfs.IsBtrfs(s.raftServer.LogPath()) {
+		btrfs.SetNOCOW(s.raftServer.LogPath())
+	}
+
 	s.findCluster(discoverURL, peers)
 
 	s.closeChan = make(chan bool)