return pi, errInvalidArgument
	}
	if idx+1 > len(z.serverPools) {
		return pi, errInvalidArgument
	}

	info := z.serverPools[idx].StorageInfo(context.Background())
	info.Backend = z.BackendInfo()

	usableTotal := int64(GetTotalUsableCapacity(info.Disks, info))
	usableFree := int64(GetTotalUsableCapacityFree(info.Disks, info))
	return poolSpaceInfo{
		Total: usableTotal,
		Free:  usableFree,