SCSI hard disk drives
"Start Unit Request Failed"

London and Manchester, UK
0870 7424 008


Start Unit Request Failed - Typical failures on SCSI hard disk drives

Common SCSI hard disk models: IBM Ultrastar, Quantum Atlas, Seagate Cheetah, + assorted and badged models from Fujitsu, Compaq and HP

Features: SCSI hard disks are often regarded as the high performance drives of the hard drive marketplace. They spin faster than their IDE counterparts, and so, data transfer speeds are often much quicker. Because of this, SCSI drives are often found in servers that have to provide a lot of data throughput. However this performance often comes at a price as mechanical failures on these devices can often prove very difficult to recover from. With IDE hard drive performance increasing all the time, many modern servers now use IDE hard drives instead of SCSI.

Background: Unlike their IDE counterparts, SCSI disks operate through their own SCSI BIOS. When the computer is powered up, the SCSI BIOS sends a "Start Unit Request" command to the SCSI devices under it's control. If the drive fails to start correctly, the SCSI drive will (often) power down and the error "Start Unit Request Failed" is displayed.

Reasons for SCSI drive failure:

  • Power down / power up: SCSI drives are often found in machines that "never" switch off. When eventually these machines are powered down, getting the SCSI drives to restart can often be difficult
  • Electronic Failure: Failure of the electronic circuitry on the hard disk will prevent the drive from starting, fortuantely drives with this type of failure are often recoverable
  • Mechanical Failure: Often characterized by a clucking sound or high pitched whine, SCSI hard disk mechanical failures are often the worst type of failure these drives can suffer. The noises, though not always apparent, are indicative of an internal mechanical failure or head crash. Drives that are suffering from these type of fault will nearly always require clean room attention. We recommend customers use our Advanced Data Recovery services to attempt data recovery on SCSI drives with this failure.
  • All the usual failures that can be found on hard disk drives eg. bad sectors, logical corruption etc.

What should I do?: Call the Data Clinic and talk your problem through with us on 0870 7424 008, or fill out our auto-form and we'll call you back

SCSI disks are often used in RAID arrays and servers. If you have a failed server please read our RAID / Server failure & data recovery section.

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Please note that all modern hard disk drives are manufactured to very high standards, fail infrequently and have very similar rates of reliability.

 

Above: An IBM Ultrastar SCSI hard disk that has suffered a severe head crash. The platters on these drives are made of glass which is in turn coated in a metallic film that holds the data in the form of a magnetic charge. In this case the read / write heads of the hard disk have come in contact with the platters and literally stripped the magnetic film from them to such an extent that it's possible to see through the top platter to the platter underneath. Not suprisingly, with failures of this kind there's little chance of a successful recovery of data.

 

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