private Synchronized() {}

  static class SynchronizedObject implements Serializable {
    final Object delegate;
    final Object mutex;

    SynchronizedObject(Object delegate, @CheckForNull Object mutex) {
      this.delegate = checkNotNull(delegate);
      this.mutex = (mutex == null) ? this : mutex;
    }

    Object delegate() {
      return delegate;
    }

    // No equals and hashCode; see ForwardingObject for details.

  private Synchronized() {}

  static class SynchronizedObject implements Serializable {
    final Object delegate;
    final Object mutex;

    SynchronizedObject(Object delegate, @CheckForNull Object mutex) {
      this.delegate = checkNotNull(delegate);
      this.mutex = (mutex == null) ? this : mutex;
    }

    Object delegate() {
      return delegate;
    }

    // No equals and hashCode; see ForwardingObject for details.

	// metrics
	LastRefreshTimeUnixNano         uint64
	LastRefreshDurationMilliseconds uint64
	TotalRefreshSuccesses           uint64
	TotalRefreshFailures            uint64

	sync.Mutex

	iamRefreshInterval time.Duration

	LDAPConfig   xldap.Config  // only valid if usersSysType is LDAPUsers
	OpenIDConfig openid.Config // only valid if OpenID is configured

		ReadData:         readData,
		InclFreeVersions: opts.InclFreeVersions,
		Healing:          false,
	}

	mrfCheck := make(chan FileInfo)
	defer xioutil.SafeClose(mrfCheck)

	var rw sync.Mutex

	// Ask for all disks first;
	go func() {
		ctx, cancel := context.WithCancel(ctx)
		defer cancel()

		wg := sync.WaitGroup{}
		for i, disk := range disks {
			if disk == nil {
				done <- false