An information system including: a first and second storage apparatus including a first and second volume; a failure detection storage apparatus including a third volume; wherein, for backup purposes, the first and second volumes form a remote copy pair, and, for I/O request purposes, are recognized as a single volume labeled with a same volume identifier, but accessible by alternative access paths designated with differing priorities; wherein, if one apparatus detects a failure in the other or a connection failure, the apparatus detecting the failure stores, in the third volume, a failure information flag showing failure; wherein, upon receiving the I/O request through the second access path, the second storage apparatus determines whether the failure information flag is stored in the third volume, and sends an error reply of the I/O request to the host computer if the failure information flag is stored in the third volume.