dmesg | grep sda revealed

Code:
SCSI device sda: 78140160 512-byte hdwr sectors (40008 MB)
sda: Write Protect is off
sda: Mode Sense: 00 3a 00 00
SCSI device sda: drive cache: write back
SCSI device sda: 78140160 512-byte hdwr sectors (40008 MB)
sda: Write Protect is off
sda: Mode Sense: 00 3a 00 00
SCSI device sda: drive cache: write back
 sda: <3>ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x2
sda: Current: sense key=0xb
end_request: I/O error, dev sda, sector 0
Buffer I/O error on device sda, logical block 0
sd 0:0:0:0: Attached scsi disk sda
I have no idea what this means or what to do next