The most common cause of this problem is unapproved hardware. Some SCSI devices for the PC market do not meet the high I/O speed requirements for the UNIX market. Other possible causes of this problem are improper cabling or termination, and power fluctuations. Data corruption is possible, but unlikely to occur, because this parity error prevents data transfer.
Check that all SCSI devices on the bus are Sun-approved hardware. Then verify that all cables measure no longer than six meters total and that all SCSI connections are properly terminated. If power fluctuations are occurring, invest in an uninterruptible power supply.