Send the SCSI WRITE SAME (10, 16 or 32 byte) command to DEVICE. This
command writes the given block NUM times to consecutive blocks on
the DEVICE starting at logical block address LBA.
The length of the block to be written multiple times is obtained from
the LEN argument, the length of the given input file IF,
or by calling READ CAPACITY(16) on DEVICE. The contents of the
block to be written are obtained from the input file IF or
zeroes are used. If READ CAPACITY(16) is called (which implies IF
was not given) and the PROT_EN bit is set then the last 8 bytes are
set to 0xff. If READ CAPACITY(16) fails then READ CAPACITY(10) is
used to determine the block size.
If neither --10, --16 nor --32 is given then
WRITE SAME(10) is sent unless one of the following conditions is met.
If LBA (plus NUM) exceeds 32 bits, NUM exceeds 65535,
or the --unmap option is given then WRITE SAME(16) is sent.
The --10, --16 and --32 options are mutually
As of SBC-3 revision 24 the UNMAP and ANCHOR bits are not supported by
WRITE SAME (10). However there is a proposal to allow that case and
this utility now allows those bits to be set for WRITE SAME (10) when
the --10 is given.
The WRITE SAME(10, 16 and 32) commands interpret a NUM of zero
as write to the end of DEVICE. This utility defaults NUM to
1 . The WRITE SAME commands have no IMMED bit so if NUM is
large (or zero) then an invocation of this utility could take a long
time, potentially as long as a FORMAT UNIT command. In such situations
the command timeout value TO may need to be increased from its
default value of 60 seconds.
As a precaution against an accidental 'sg_write_same /dev/sda' (for example)
overwriting LBA 0 on /dev/sda with zeroes, at least one of the
--in=IF, --lba=LBA or --num=NUM options must be
given. Obviously this utility can destroy a lot of user data so check the
Arguments to long options are mandatory for short options as well.
send a SCSI WRITE SAME (10) command to DEVICE. This option has been
added to allow the --unmap (and --anchor) options to be
set on the SCSI WRITE SAME (10) command. As of the SBC-3 revision 25
draft this has been proposed but hasn't be accepted.
send a SCSI WRITE SAME (16) command to DEVICE.
send a SCSI WRITE SAME (32) command to DEVICE.
sets the ANCHOR bit in the cdb. Introduced in SBC-3 revision 22.
That draft requires the --unmap option to also be specified.
sets the 'Group number' field to GN. Defaults to a value of zero.
GN should be a value between 0 and 31.
output the usage message then exit.
read data (binary) from file named IF and use it as the data out
buffer for the SCSI WRITE SAME command. The length of the data out buffer
is --xferlen=LEN or, if that is not given, the length of the IF
file. If IF is "-" then stdin is read. If this option is not given
then 0x00 bytes are used as fill with the length of the data out buffer
obtained from --xferlen=LEN or by calling READ CAPACITY(16 or 10).
If the response to READ CAPACITY(16) has the PROT_EN bit set then data
out buffer size is modified accordingly with the last 8 bytes set to 0xff.
where LBA is the logical block address to start the WRITE SAME command.
Defaults to lba 0 which is a dangerous block to overwrite on a disk that is
in use. Assumed to be in decimal unless prefixed with '0x' or has a
sets the LBDATA bit in the WRITE SAME cdb.
where NUM is the number of blocks, starting at LBA, to write the
data out buffer to. The default value for NUM is 1. The value corresponds
to the 'Number of logical blocks' field in the WRITE SAME cdb. Note that a
value of 0 in NUM is interpreted as write the data out buffer on every
block starting at LBA to the end of the DEVICE.
sets the PBDATA bit in the WRITE SAME cdb.
where TO is the command timeout value in seconds. The default value is
60 seconds. If NUM is large (or zero) a WRITE SAME command may require
considerably more time than 60 seconds to complete.
sets the UNMAP bit in the WRITE SAME(10, 16 and 32) cdb. See UNMAP section
increase the degree of verbosity (debug messages).
output version string then exit.
sets the "Write protect" field in the WRITE SAME cdb to WPR. The
default value is zero. WPR should be a value between 0 and 7.
where LEN is the data out buffer length. Defaults to the length of
the IF file or, if that is not given, then the READ CAPACITY(16 or 10)
command is called on the DEVICE and the 'Logical block length in
bytes' and the PROT_EN bit in the response are used to determine the
data out buffer length. If both this option and the IF option are
given and LEN exceeds the length of the IF file then LEN
is the data out buffer length with zeroes used as pad bytes.
Logical block provisioning is the complicated term used in SBC-3 revision
25 for the ability to mark blocks as unused. It is closely related to the
ATA DATA SET MANAGEMENT command with the "Trim" bit set. For large
storage arrays, it is a way to provision less physical storage than the
READ CAPACITY command reports is available, potentially allocating more
physical storage when WRITE commands require it. For flash memory it is
a way of potentially saving power (and perhaps access time) when it is
known large sections (or almost all) of the flash memory is not in use.
Support for logical block provisioning is indicated by the LBPME bit being
set in the READ CAPACITY(16) command response (see the sg_readcap utility).
That implies at least one of the UNMAP or WRITE SAME(16) commands is
implemented. If the UNMAP command is implemented then
the "Maximum unmap LBA count" and "Maximum unmap block descriptor count"
fields in the Block Limits VPD page should both be greater than zero. The
READ CAPACITY(16) command response also contains a LBPRZ bit which if set
means that if unmapped blocks are read then zeroes will be returned for the
data (and if protection information is active, 0xff bytes are returned for
When the UNMAP bit is set in the cdb then the data out buffer is also sent.
Additionally the data section of that data out buffer should be full of 0x0
bytes while the data protection block, 8 bytes at the end if present, should
be set to 0xff bytes. If these conditions are not met and the LBPRZ bit is
set then the UNMAP bit is ignored and the data out buffer is written to the
DEVICE as if the UNMAP bit was zero. In the absence of the
--in=IF option, this utility will attempt build a data out buffer
that meets the requirements for the UNMAP bit in the cdb to be acted on by
Logical blocks may also be unmapped by the SCSI UNMAP and FORMAT UNIT
commands (see the sg_unmap and sg_format utilities).
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.
The exit status of sg_write_same is 0 when it is successful. Otherwise see
the sg3_utils(8) man page.