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| sudo diskutil unmount /dev/disk2s1 sudo diskutil unmount /dev/disk3s1 sudo dd bs=1m if = /dev/disk2 of= /dev/disk3 |
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| sudo pkill -INFO dd # mac系统 sudo killall -USR1 dd # linux系统 3+0 records in 2+0 records out 20971520 bytes transferred in 39.393646 secs (532358 bytes /sec ) |
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| CTRL + T |
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| pv -tpreb /dev/sda | dd of= /dev/sdb bs=1M |
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| while pgrep ^ dd ; do pkill -INFO dd ; sleep 10; done |
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| while killall -USR1 dd ; do sleep 5; done |
我这样用dd一个多小时后,8G大小的SD卡才复制2G多一点。觉得太慢了,然后上网查了怎么speed up,有人说加大bs=1m这个参数会有作用:
Adjusting the bs parameter can increase the speed, for example, I have 2 HDD that I know have a read/write speed greater than 100 MB/s so I do this:
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| dd if = /dev/sda of= /dev/sdb bs=100M |
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| pv < /dev/sda > /dev/sdb |
当我调整bs=1m,到bs=10m时,再次试验 ,发现速度根本没有太大变化。
后来再找资料,发现跟mac系统本身有关系。把 /dev/disk2 修改成 /dev/rdisk2 就会快了。
参考 :http://apple.stackexchange.com/questions/56159/how-can-i-speed-up-sd-card-writing-speed-using-dev-disk-on-a-macbook-pro
参考 :http://daoyuan.li/solution-dd-too-slow-on-mac-os-x
下面这样会快上几十倍:
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| sudo dd bs=10m if = /dev/rdisk2 of= /dev/rdisk3 21:22:25 2+0 records in 1+0 records out 10485760 bytes transferred in 4.558941 secs (2300043 bytes /sec ) 6+0 records in 5+0 records out 52428800 bytes transferred in 14.382413 secs (3645341 bytes /sec ) 212+0 records in 211+0 records out 2212495360 bytes transferred in 523.833141 secs (4223664 bytes /sec ) |
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