sg_read_long - send a SCSI READ LONG command
sg_read_long [--16] [--correct] [--help] [--lba=LBA] [--out=OF]
[--pblock] [--verbose] [--version] [--xfer_len=BTL] DEVICE
Send SCSI READ LONG command to DEVICE. The read buffer is output in hex
and ASCII to stdout or placed in a file. Note that the data returned
includes the logical block data (typically 512 bytes for a disk) plus
ECC information (whose format is proprietary) plus optionally other
Arguments to long options are mandatory for short options as well.
uses a SCSI READ LONG(16) command. The default action is to use
a SCSI READ LONG(10) command. The READ LONG(10) command has a 32
bit field for the lba while READ LONG(16) has a 64 bit field.
sets the ’CORRCT’ bit in the SCSI READ LONG command. When set
the data is corrected by the ECC before being transferred back
to this utility. The default is to leave the ’CORRCT’ bit clear
in which case the data is not corrected.
output the usage message then exit.
where LBA is the logical block address of the sector to read.
Assumed to be in decimal unless prefixed with ’0x’ (or has a
trailing ’h’). Defaults to lba 0. If the lba is larger than can
fit in 32 bits then the --16 option should be used.
instead of outputting ASCII hex to stdout, send it in binary to
the file called OF. If ’-’ is given for OF then the (binary)
output is sent to stdout. Note that all informative and error
output is sent to stderr.
sets the ’PBLOCK’ bit in the SCSI READ LONG command. When set
the physical block (plus ECC data) containing the requested
logical block address is read. The default is to leave the
’PBLOCK’ bit clear in which case the logical block (plus any ECC
data) is read.
increase the level of verbosity, (i.e. debug output).
print the version string and then exit.
where BTL is the byte transfer length (default to 520). If the
given value (or the default) does not match the "long" block
size of the device, the appropriate BTL is deduced from the
error response and printed (to stderr). The idea is that the
user will retry this utility with the correct transfer length.
If a defective block is found and its contents, if any, has been
retrieved then "sg_reassign" could be used to map out the defective
block. Associated with such an action the number of elements in the
"grown" defect list could be monitored (with "sg_reassign --grown") as
the disk could be nearing the end of its useful lifetime.
Various numeric arguments (e.g. LBA) may include multiplicative
suffixes or be given in hexadecimal. See the "NUMERIC ARGUMENTS"
section in the sg3_utils(8) man page.
As a data point, Fujitsu uses a 54 byte ECC (per block) which is
capable of correcting up to a single burst error or 216 bits "on the
fly". [Information obtained from MAV20xxrc product manual.]
The exit status of sg_read_long is 0 when it is successful. Otherwise
see the sg3_utils(8) man page.
Written by Douglas Gilbert.
Report bugs to <dgilbert at interlog dot com>.
Copyright © 2004-2007 Douglas Gilbert
This software is distributed under the GPL version 2. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
sg_reassign, sg_write_long, sg_dd