Enterprise-class versus Desktop-class Hard Drives

Enterprise-class versus Desktop-class Hard Drives
Revision 1.0
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1.1.4.5 Data Integrity
One feature of an enterprise-class system is the implementation of “end-to-end” error detection.
Transmitted data is accompanied by parity or checksum at every stage of transmission within
the system. This allows data transmission errors to be detected, and in some cases corrected
or retransmitted. Although desktop systems do have error detection in some subsystems, they
do not usually provide this end-to-end data protection. For example desktop systems do not
usually incorporate Error Correction Code (ECC) in system memory or drive memory buffers.
Enterprise class systems use error detection at every data transmission stage within the system,
including ECC support in system memory and drive memory buffers. Refer to the illustration
below for more information.
Figure 2: Data Protection Within the Hard Drive Electronics
Enterprise class drives use ECC for data passing through drive memory and may use additional
error detection methods for data transmitted within the drive electronics. The form of this error
detection and correction capability is usually proprietary to the drive vendor. Desktop drives do
not have this data protection feature within drive memory, If a data error occurs in memory it
will not be detected. The error will be transmitted to the next stage in the drive electronics, and
the error will be propagated to the drive media or to the host device. This type of error becomes
very difficult to detect and can affect operating system stability or client data reliability.
Interface
Logic
Memory
Buffer
Formatter
Memory Buffer /
Disk Interaction
To Disk
•Receive memory
buffer data, check ECC
•If ECC error then
pass error back to
buffer
•Remove buffer ECC,
format data, and add
Disk Checksum
•Write to disk, manage
errors
From Disk
•Check and remove
checksum
•Manage errors
•Add Memory ECC
•Pass to buffer
Host Data Interaction
From Host
•Data and CRC received
•If CRC error then pass error
back to host
•CRC stripped and ECC added
•Data passed to buffer
To Host
•Data received from buffer
•If ECC error then pass error
back to buffer
•ECC Parity is stripped off and
CRC added
•Data passed to host
Once data written
to disk, status
complete sent to
host
DATA
Memory Buffer
ECC or Non-ECC
Disk
ECC Memory
only in
Enterprise
Class Drives