diff options
Diffstat (limited to 'sg_dd.8')
| -rw-r--r-- | sg_dd.8 | 44 |
1 files changed, 35 insertions, 9 deletions
@@ -1,6 +1,6 @@ -.TH SG_DD "8" "September 2001" "sg3_utils-0.95" SG3_UTILS +.TH SG_DD "8" "February 2002" "sg3_utils-0.98" SG3_UTILS .SH NAME -copies data to and from sg and raw devices +sg_dd \- copies data to and from sg and raw devices .SH SYNOPSIS .B sg_dd [\fIOPTION\fR]... @@ -25,6 +25,10 @@ which permits "bs" to be an integral multiple. Default is 512 which is usually correct for disks but incorrect for cdroms (which normally have 2048 byte blocks). .TP +cdbsz=6 | 10 | 12 | 16 +size of SCSI READ and/or WRITE commands issued on sg device names. +Default is 10 byte SCSI command blocks +.TP count=BLOCKS copy this number of blocks. Default is minimum number that sg devices return from READ CAPACITY (if that works) or 0 @@ -35,6 +39,10 @@ IO which, if not available, falls back to indirect IO and notes this at completion. If direct IO is selected and /proc/scsi/sg/allow_dio has the value of 0 then a warning is issued (and indirect IO is performed) .TP +gen=0 | 1 +the default action (when "gen=0") is to require that either "if" or "of" +is a sg or raw device name. To remove this restriction set "gen=1" +.TP ibs=BYTES if given must be the same as bs .TP @@ -52,14 +60,22 @@ skip BLOCKS bs-sized blocks at start of output .TP skip=BLOCKS skip BLOCKS bs-sized blocks at start of input +.TP +time=0 | 1 +when 1, times transfer and does throughput calculation, outputting the +results (to stderr) at completion. When 0 (default) doesn't perform timing +.TP +--version +outputs version number information and exits .PP -Either the input file or the output file must be a sg or raw device. +Either the input file or the output file must be a sg or raw device, +unless "gen=1". A raw device must be bound to a block device prior to using sg_dd. See .B raw(8) for more information about binding raw devices. To be safe, the sg device -mapping to SCSI block devices should be checked with "cat /proc/scsi/scsi" -before use. +mapping to SCSI block devices should be checked with "cat /proc/scsi/scsi", +or sg_map before use. .PP The count is only deduced for sg devices (minimum > 0 if both input and output are sg devices) otherwise it defaults to 0. This is for safety! @@ -77,10 +93,11 @@ this data into user memory (write operations reverse this sequence). This is called "indirect IO" and there is a "dio" option to select "direct IO" which will DMA directly into user memory. Due to some issues "direct IO" is disabled in the sg driver and needs a -configuration change to activate it. +configuration change to activate it. This is typically done with +"echo 1 > /proc/scsi/sg/allow_dio". .PP All informative, warning and error output is sent to stderr so that -dd\'s output file can be stdout and remain unpolluted. If no options +dd's output file can be stdout and remain unpolluted. If no options are given, then the usage message is output and nothing else happens. .SH EXAMPLES .PP @@ -95,7 +112,7 @@ equivalent to: .PP dd if=/dev/sda of=t bs=512 count=1000000 .PP -although dd\'s speed may improve if bs was larger and count was suitably +although dd's speed may improve if bs was larger and count was suitably reduced. Using a raw device to do something similar on a IDE disk: .PP raw /dev/raw/raw1 /dev/hda @@ -112,6 +129,15 @@ This assumes a valid partition is found on the SCSI disk at the given skip block address (past the 5 GB point of that disk) and that the partition goes to the end of the SCSI disk. An explicit count is probably a safer option. +.PP +To time a streaming read of the first 1 GB on a disk this command +could be used: +.PP + sg_dd if=/dev/sg0 of=/dev/null bs=512 count=2m time=1 +.PP +On completion this will output a line like: +"time to transfer data was 26.020794 secs, 41.26 MB/sec". The "MB/sec" +in this case is 1,000,000 bytes per second. .SH NOTE For sg devices this command issues READ_10 and WRITE_10 SCSI commands which are appropriate for disks and CDROM players. Those commands are not @@ -128,7 +154,7 @@ Written by Doug Gilbert and Peter Allworth. .SH "REPORTING BUGS" Report bugs to <dgilbert@interlog.com>. .SH COPYRIGHT -Copyright \(co 2000, 2001 Douglas Gilbert +Copyright \(co 2000-2002 Douglas Gilbert .br This software is distributed under the GPL version 2. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |