Mode page 1, ECC correction span field expansion?

Gerry_Houlder at Gerry_Houlder at
Fri Feb 12 12:53:16 PST 1999

* From the T10 Reflector (t10 at, posted by:
* Gerry_Houlder at
Mode page 1 provides one byte for ECC Correction Span. This has been
adequate until now, but there are products on the horizon that will have
correction span of more than 255 bits (this is the maximum that can be
expressed with one byte. Should this field be expanded? if so, how?

(a) We could just define 0xFF as meaning "255 or more bits correction
capability". If the system companies (i.e., buyers of direct access
devices) never use this field, perhaps this is explanation enough.

(b) A value of 0xFF could be used as a pointer to another (new) field in
mode page 1 that provides two bytes to describe the ECC correction span.

(c) Since the ECC correction span tends to be an unchangeable value, we
could define an Inquiry VPD page that reports the actual ECC Correction
Span and maybe some other numbers as well. The values reported on this page
would be the maximum, and the one byte values on Mode Page 1 could be
redefined to be "percent of maximum" with 0xFF being 100% and lower values
in increments of 1/256 of the maximum.

(d) Make your own suggestion on the reflector.

I would like to have discussion of this issue at the next working group
meeting in Harrisburg, PA in March. John Lohmeyer, please add this to the
agenda. If there is reflector discussion that seems to converge on a
solution we won't have to spend much meeting time on it.

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