Method and apparatus for detecting and correcting errors in stored information
View Patent ↗A device can receive information to be stored in a first part of a first portion of a block, read previously-stored information from a second part, and store the specified information in the first part and simulate storage of the previously-stored information in the second part while generating error detection information which is then stored in a second portion of the block. The device can read a specified subset of sections in a block, use part of each section to detect and/or correct an error in another part thereof, while avoiding reading the error detection information unless a section in the subset has an uncorrected error. Detected errors are corrected with successive correction stages, while maintaining for each section being processed in the stages a count of the number of other sections which are thereafter read in succession without error.
1. An apparatus, comprising:
a storage portion which a plurality of blocks, each block including a data portion and a residue portion,
wherein the residue portion is used to store block-level error correction information corresponding to information stored in the data portion;
a circuit portion which includes instructions stored therein to:
write information to and read information from said storage portion, and
perform a simulated write to said storage portion wherein no information is actually written; said circuit portion including:
a block-level error correction generator portion configured to generate block-level error correction information when said circuit portion writes information to said storage portion, and generate block-level error correction information when said circuit portion performs a simulated write to said storage portion; and
a sector-level error correction generator portion configured to generate sector-level error correction information when said circuit portion writes information to said storage portion;
wherein said circuit portion includes instructions stored therein to:
receive user data to be stored in a first part of the data portion of a specified block;
read previously-stored user data from a second part of the data portion of the specified block and buffering the user data from the second part of the data portion the specified block, wherein the second part includes all of the data portion of the specified block other than the first part thereof;
write the received user data to the first part of the data portion of the specified block, causing said sector-level error correction generator portion to generate sector-level error correction information corresponding to the received user data, and causing said block-level error correction generator portion to generate block-level error correction information corresponding to the received user data;
write the sector-level error correction information to the first part of the data portion of the specified block;
perform a simulated write of the previously-stored user data to the second part of the data portion of the specified block, causing said block-level error correction generator portion to generate block-level error correction information corresponding to the previously-stored user data; and
write the block-level error correction information corresponding to the received user data and the previously-stored user data to the residue portion of the specified block.
2. An apparatus according to claim 1 , wherein said circuit portion includes instructions stored therein to:
write the received user data in its entirety to the first part of the data portion of the specified block, and
perform a simulated write of the previously-stored user data in its entirety to the second part of the data portion of the specified block.
3. An apparatus according to claim 1 , wherein:
the previously-stored user data of the second part of the data portion of the specified block includes first and second segments; and
said circuit portion includes instructions stored therein to:
perform a simulated write of the first segment in its entirety to the second part of the data portion of the specified block,
write the received user data in its entirety to the first part of the data portion of the specified block, and
perform a simulated write of the second segment in its entirety to the second part of the data portion of the specified block.
4. An apparatus according to claim 1 , wherein
said circuit portion includes instructions stored therein to:
perform a simulated write of the previously-stored user data in its entirety to the second part, and
write the received user data in its entirety to the first part.
5. An apparatus according to claim 1 , wherein:
said storage portion includes a rotatable disk with a plurality of tracks; and
the plurality of tracks includes a plurality of concentric tracks.
6. An apparatus according to claim 1 , wherein said circuit portion includes instructions stored therein to:
pause said block-level error correction generator portion on the occurrence of an exception while said block-level error correction generator portion is generating the block-level error correction information,
restart a write of the received user data to the first part of the data portion of the specified block and perform a simulated write of the previously-stored user data to the second part of the specified block, and
enable said block-level error correction generator portion at the point in the process which corresponds to the occurrence of the exception.
7. The apparatus of claim 1 , wherein:
the data portion of each block includes a plurality of sectors; and
the residue portion of each block includes another plurality of sectors.
8. A method of operating an apparatus having a storage portion which includes a plurality of blocks, each block including a data portion, and a residue portion used to store information facilitating corrections of errors in information stored in the data portion, the method comprising:
receiving user data to be written to a first part of the data portion of a specified block;
reading previously-stored user data from a second part of the data portion of the specified block and buffering the user data from the second part of the data portion of the specified block, wherein the second part includes all of the data of the specified block other than said first part thereof;
writing the received user data to the first part, causing a generation of block-level and sector-level error correction information corresponding to the received user data;
writing the sector-level error correction information to the first part;
simulating a writing of the previously-stored user data to the second part, causing a generation of block-level error correction information corresponding to the previously-stored user data without actually writing the previously-stored user data to the second part; and
writing the block-level error correction information corresponding to the received user data and the previously-stored user data to the residue portion of the specified block.
9. A method according to claim 8 , wherein said writing of received user data and said simulating a writing of the previously-stored user data is carried out by writing the received user data in its entirety to the first part, and simulating the writing of the previously-stored user data in its entirety to the second part.
10. A method according to claim 8 , wherein:
the previously-stored user data from the second part of the data portion includes first and second segments; and
said writing of the received user data and said simulating a writing of the previously-stored user data is carried out by:
simulating a writing of the first segment in its entirety to the second part of the data portion of the specified block, writing the received user data in its entirety to the first part of the data portion of the specified block, and
simulating a writing of the second segment in its entirety to the second part of the data portion of the specified block.
11. A method according to claim 8 , wherein said writing of the received user data and said simulating a writing of the previously-stored user data is carried out by simulating a writing of the previously-stored user data in its entirety to the first part of the data portion of the specified block, and writing the received user data in its entirety to the second part of the data portion of the specified block.
12. A method according to claim 8 , including:
responding to an occurrence of an exception during said generating of said error correction information by:
pausing the generation of the block-level error correction information,
restarting said writing of the received user data to the first part and said simulating a writing of the previously-stored user data to the second part, and
enabling the generation of the block-level error correction information at the point in the process which corresponds to the occurrence of said exception.
13. A method according to claim 8 , including carrying out said simulating a writing of the previously-stored user data in less time than would be needed for actually writing the previously-stored user data to the second part.
14. The method of claim 8 , wherein no further reading is performed after said reading.