1. A method for correcting unrecoverable errors on storage devices connected to a storage system, the method comprising: identifying, by the storage system during a data access request to the storage devices, a data block having an unrecoverable error, the unrecoverable error cannot be corrected by an underlying RAID protection technique at the storage system; providing an indicator within a close proximity of the data block having the unrecoverable error that the data block is invalid, the indicator stored at a location so that when an I/O is issued to the data block having the unrecoverable error, the indicator is read as part of the same I/O; protecting the indicator by the underlying RAID protection technique; and recovering the data block having the unrecoverable error without initiating a consistency check operation in the storage system by obtaining a good copy of the data block having the unrecoverable error asynchronously to the data access request to the storage devices during which the data block having the unrecoverable error was identified.