US 12,124,740 B2
Selective hard and soft rewrites
Ernest Stewart Gale, Tucson, AZ (US); Roy Cideciyan, Rueschlikon (CH); Simeon Furrer, Altdorf (CH); Masayuki Iwanaga, Urayasu (JP); and Keisuke Tanaka, Tokyo (JP)
Assigned to International Business Machines Corporation, Armonk, NY (US)
Filed by International Business Machines Corporation, Armonk, NY (US)
Filed on Oct. 24, 2022, as Appl. No. 17/971,675.
Prior Publication US 2024/0134565 A1, Apr. 25, 2024
Prior Publication US 2024/0231683 A9, Jul. 11, 2024
Int. Cl. G06F 3/06 (2006.01)
CPC G06F 3/0659 (2013.01) [G06F 3/0619 (2013.01); G06F 3/064 (2013.01); G06F 3/0676 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A system comprising:
a magnetic head;
a controller communicatively coupled to the magnetic head, wherein the controller is adapted to:
write, using the magnetic head, a data set to a sequential access medium, the data set comprising a plurality of encoded data blocks;
classify the encoded data blocks into three or more classes of write quality, wherein the three or more classes of write quality comprise a hard rewrite class for which rewrites are necessary to prevent data loss, a soft rewrite class for which rewrites are desirable but not necessary, and a no rewrite class for which no rewrite is needed or desired, wherein the encoded data blocks are classified in the hard rewrite class if:
a number of run length limited decoding errors is greater than a first predetermined threshold;
and either:
a number of byte errors is greater than a second predetermined threshold; or
an uncorrectable error is detected; and
selectively rewrite one or more of the encoded data blocks in a rewrite area of the sequential access medium based at least in part on the write quality class.