dd question

William A. Mahaffey III wam at hiwaay.net
Sat Sep 26 14:00:35 UTC 2015

I am preparing a USB stick for use to install FreeBSD 9.3R on 2 new 
boxen I am bringing online. I already had the FreeBSD 9.3R img dd'ed to 
that stick last year when I provisioned this box, but for some reason, 
when I plugged the stick into my USB port today to copy some additional 
files to it (scripts to be used during installs to partition & slice up 
HDD's), I got errors in my syslog file & couldn't mount the drive for 
the copies. No problema, I'll just re-dd the image to the device & start 
over, all I would lose is output from the previous install (this box, 
last year this time). However, I notice the dd is proceeding *VERY* slowly:

[root at kabini1, /etc, 8:47:59am] 508 % ll /dev/da0*
crw-r-----  1 root  operator  0xd2 Sep 26 08:29 /dev/da0
crw-r-----  1 root  operator  0xcd Sep 26 08:29 /dev/da0a
[root at kabini1, /etc, 8:48:09am] 509 % ll 
total 1530556
-rw-r--r--  1 wam  users  178749440 Jul 26  2014 
-rw-r--r--  1 wam  users  671152128 Jul 26  2014 
-rw-r--r--  1 wam  users  717373440 Jul 26  2014 
-rw-------  1 wam  users        811 Jul 26  2014 checksum.MD5.txt
[root at kabini1, /etc, 8:48:19am] 510 % dd 
94834+0 records in
94834+0 records out
48555008 bytes transferred in 542.035379 secs (89579 bytes/sec)
101599+0 records in
101599+0 records out
52018688 bytes transferred in 580.466607 secs (89615 bytes/sec)

I got that output by sending the SIGINFO signal to the dd process from 
another shell window. My question is: Why so slow (89-ish KB/s) ? I have 
gigabit switched LAN (125 MB/s theoretical speed), & most other file 
copies or rsyncs across the LAN go at about 1/3 - 1/2 of theoretical 
speeds, which is AOK by me. Any ideas ? TIA & have a nice weekend.


	William A. Mahaffey III


	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                            -- Gen. George S. Patton Jr.

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