Quantum FIREBALL PLUS AS 10.2 User Manual

Basic Principles of Operation
Quantum Fireball Plus AS 10.2/20.5/30.0/40.0/60.0 GB AT 5-14
The drive does not need to re-read a sector on the next disk revolution or apply ECC
for those errors that are corrected on-the-fly. Errors corrected in this manner are
invisible to the host system.
When errors cannot be corrected on-the-fly, an automatic retry, and a more rigorous
16 10-bit symbols error correction algorithm enables the correction of any sector
with single bursts (up to 16 contiguous 10-bit symbols), or up to 16 multiple
random one 10-bit symbol burst errors. In addition to this error correction
capability, the drive’s implementation of an additional cross-checking code and
algorithm double checks the main ECC correction, and greatly decreases the
likelihood of miscorrection.
The 32 ECC check symbols shown in Figure 5-4 are used to detect and correct
errors. The cross-checking and ECC data is computed and appended to the user
data when the sector is first written.
Figure 5-4
Figure 5-4 Figure 5-4
Figure 5-4 Sector Data Field with ECC Check Bytes
Because the ECC check symbols follow the cross checking bytes, errors found
within the cross-checking bytes can be corrected. Due to the power and
sophistication of the code, errors found within the ECC check bytes can also be
corrected.
Each time a sector of data is read, the Quantum Fireball Plus AS drives will
generate a new set of ECC check symbols and cross-checking bytes from the user
data. These new check symbols are compared to the ones originally written to the
disk. The difference between the newly computed and original check symbols is
reflected in a set of 32 syndromes and three cross checking syndromes, which
correspond to the number of check symbols. If all the ECC syndrome values equal
zero, and cx syndrome value equals zero or 0FF, the data was read with no errors,
and the sector is transferred to the host system. If any of the syndromes do not equal
zero or OFF, an error has occurred. The type of correction the drive applies depends
on the nature and the extent of the error.
High speed on-the-fly error correction saves several milliseconds because there is
no need to wait for a disk revolution to bring the sector under the head for re-
reading.
5.3.3.2
5.3.3.25.3.3.2
5.3.3.2 ECC Error Handling
ECC Error HandlingECC Error Handling
ECC Error Handling
When a data error occurs, the Quantum Fireball Plus AS hard disk drives check to
see if the error is correctable on-the-fly. This process takes about 200 µs. If the error
is correctable on-the-fly, the error is corrected and the data is transferred to the host
system.
If the data is not correctable on-the-fly, the sector is re-read in an attempt to read
the data correctly without applying firmware ECC correction. Before invoking the

Quantum FIREBALL PLUS AS 10.2 Specifications

General

Brand	Quantum
Model	FIREBALL PLUS AS 10.2
Category	Storage
Language	English