diff options
Diffstat (limited to 'doc/sg_write_same.8')
| -rw-r--r-- | doc/sg_write_same.8 | 36 |
1 files changed, 31 insertions, 5 deletions
diff --git a/doc/sg_write_same.8 b/doc/sg_write_same.8 index 55dcfec9..1a9d4fff 100644 --- a/doc/sg_write_same.8 +++ b/doc/sg_write_same.8 @@ -1,4 +1,4 @@ -.TH SG_WRITE_SAME "8" "December 2019" "sg3_utils\-1.45" SG3_UTILS +.TH SG_WRITE_SAME "8" "June 2020" "sg3_utils\-1.45" SG3_UTILS .SH NAME sg_write_same \- send SCSI WRITE SAME command .SH SYNOPSIS @@ -124,6 +124,10 @@ sets the NDOB bit in the WRITE SAME (16 and 32 byte) commands. NDOB stands for No Data\-Out Buffer. Default is to clear this bit. When this option is given then \fI\-\-in=IF\fR is not allowed and \fI\-\-xferlen=LEN\fR can only be given if \fILEN\fR is 0 . +.br +By default zeros are written in each block, but it is possible that +the "provisioning initialization pattern" is written depending on other +settings. .TP \fB\-n\fR, \fB\-\-num\fR=\fINUM\fR where \fINUM\fR is the number of blocks, starting at \fILBA\fR, to write the @@ -235,7 +239,11 @@ introduction in lk 2.6.28 . The exit status of sg_write_same is 0 when it is successful. Otherwise see the sg3_utils(8) man page. .SH EXAMPLES -One simple usage is to write blocks of zero from (and including) a given LBA: +BEWARE: all these examples will overwrite the data on one or more blocks, +potentially CLEARING the WHOLE DISK. +.PP +One simple usage is to write blocks of zero from (and including) a given LBA +for 63 blocks: .PP sg_write_same \-\-lba=0x1234 \-\-num=63 /dev/sdc .PP @@ -246,7 +254,24 @@ of bytes in a logical block. Let us assume that is 512 bytes. Since of zeros (each block containing 512 bytes) will be written from (and including) LBA 0x1234 . Note that only one block of zeros is passed to the SCSI WRITE SAME command in the data\-out buffer (as required by -SBC\-3). +SBC\-3). Using the WRITE SAME SCSI command to write one or more blocks +blocks of zeros is equivalent to the NVMe command: Write Zeroes. +.br +Now we will write zero blocks to the WHOLE disk. [Note sanitize type +commands will also clear blocks and metdata that are not directly +visible]: +.PP + sg_write_same \-\-lba=0x0 \-\-num=0 /dev/sdc +.PP +Yes, in this context \-\-num=0 means the rest of the disk. The above +invocation may give an error due to the WSNZ bit in the Block Limits VPD +page being set. To get around that try: +.PP + sg_write_same \-\-lba=0x0 \-\-ndob /dev/sdc +.PP +this invocation, if supported, has the added benefit of not sending a data +out buffer of zeros. Notes that it is possible that the "provisioning +initialization pattern" is written to each block instead of zeros. .PP A similar example follows but in this case the blocks are "unmapped" ("trimmed" in ATA speak) rather than zeroed: @@ -322,9 +347,10 @@ Written by Douglas Gilbert. .SH "REPORTING BUGS" Report bugs to <dgilbert at interlog dot com>. .SH COPYRIGHT -Copyright \(co 2009\-2019 Douglas Gilbert +Copyright \(co 2009\-2020 Douglas Gilbert .br This software is distributed under a FreeBSD license. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. .SH "SEE ALSO" -.B sg_format,sg_get_lba_status,sg_readcap,sg_vpd,sg_unmap(sg3_utils) +.B sg_format,sg_get_lba_status,sg_readcap,sg_vpd,sg_unmap, +.B sg_write_x(sg3_utils) |