HDD Implementation Of RC (Read Continuous)
Tom Wicklund
wicklund at intellistor.com
Fri Nov 15 15:52:37 PST 1996
* From the SCSI Reflector (scsi at symbios.com), posted by:
* wicklund at Intellistor.COM (Tom Wicklund)
*
Tom Gardner writes:
> Has there been any discussion of the actual implementation of the Read
> Continuous bit. As an old DASD hand (that old!) I'm extremely
> reluctant to ever send bad data to the host without immediately so
> stating. However the spec seems to permit it.
>
> The question is are HDD's which support RC really sending bad data or
> just using the RC as a global switch to minimize the length of error
> recovery.
Traditionally (at least from markets I worked in) RC means no error
correction. Users who turn on RC are those who don't care about a few
bits in error but care greatly about lost performance, for instance
imaging applications which store real time video. A few bit error
might show up as a pixel or two wrong, but this isn't a big deal at 30
frames / second. Video is less tolerant today though since
compression means that bit errors are now important.
Thomas Wicklund
*
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