DISK I/O ERROR occuring in /var/log/messages

I am copying the oracle 11g database data files and getting the below error (File I/O Error. Please help I am unable to copy the consistant backup of my database. I tried dd, cp, ftp, scp but unable to copy the two files.

Aug 20 12:24:16 r12oraprod kernel: sd 0:2:0:0: [sda] Unhandled error code
Aug 20 12:24:16 r12oraprod kernel: sd 0:2:0:0: [sda] Result: hostbyte=DID_ERROR driverbyte=DRIVER_OK
Aug 20 12:24:16 r12oraprod kernel: sd 0:2:0:0: [sda] CDB: Read(10): 28 00 ce 86 7b a0 00 00 30 00
Aug 20 12:24:16 r12oraprod kernel: end_request: I/O error, dev sda, sector 3464919968
Aug 20 12:24:16 r12oraprod kernel: sd 0:2:0:0: [sda] Unhandled error code
Aug 20 12:24:16 r12oraprod kernel: sd 0:2:0:0: [sda] Result: hostbyte=DID_ERROR driverbyte=DRIVER_OK
Aug 20 12:24:16 r12oraprod kernel: sd 0:2:0:0: [sda] CDB: Read(10): 28 00 ce 86 7b a0 00 00 08 00
Aug 20 12:24:16 r12oraprod kernel: end_request: I/O error, dev sda, sector 3464919968
Aug 20 12:24:16 r12oraprod avahi-daemon[4663]: Invalid query packet.
Aug 20 12:24:34 r12oraprod last message repeated 261 times
Aug 20 12:25:01 r12oraprod kernel: CIFS: Unknown mount option umask
Aug 20 12:25:01 r12oraprod avahi-daemon[4663]: Invalid query packet.
Aug 20 12:25:09 r12oraprod last message repeated 76 times
Aug 20 12:25:11 r12oraprod kernel: CIFS VFS: Error connecting to socket. Aborting operation
Aug 20 12:25:11 r12oraprod kernel: CIFS VFS: cifs_mount failed w/return code = -115
Aug 20 12:25:12 r12oraprod avahi-daemon[4663]: Invalid query packet.
Aug 20 12:25:17 r12oraprod kernel: CIFS VFS: Error connecting to socket. Aborting operation
Aug 20 12:25:17 r12oraprod kernel: CIFS VFS: cifs_mount failed w/return code = -113