multi: add minimum disk space check

healthcheck/diskcheck.go

@@ -0,0 +1,18 @@
+// +build !windows,!solaris
+
+package healthcheck
+
+import "syscall"
+
+// AvailableDiskSpace returns ratio of available disk space to total capacity.
+func AvailableDiskSpace(path string) (float64, error) {
+	s := syscall.Statfs_t{}
+	err := syscall.Statfs(path, &s)
+	if err != nil {
+		return 0, err
+	}
+
+	// Calculate our free blocks/total blocks to get our total ratio of
+	// free blocks.
+	return float64(s.Bfree) / float64(s.Blocks), nil
+}