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最近碰到了一个问题.
在三台不同的机上,运行同一个脚本,在运行到dd这句时,速度差了非常多.(我dd语句的参数bs都是取1)
脚本运行的目录,均为/home/gy/job目录下,dd的输出文件也是放在目录下,dd的输入文件,则是放在/data目录下
语句: dd if=$1 of=$dp bs=1 skip=$(($(wc -c "$1"|awk '{print $1}')-2048+11)) count=12
/***********************************/
机器1:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/VolGroup_ID_29812-LogVol1
119339260 34774080 78503100 31% /
/dev/sda3 194449 14214 170195 8% /boot
none 994808 0 994808 0% /dev/shm
/dev/mapper/VolGroup_ID_29812-LogVol3
6386192 3171924 2889868 53% /usr
/dev/mapper/VolGroup_ID_29812-LogVolHome
10321208 4572636 5224284 47% /home
/***********************************/
/***********************************/
机器2:
Filesystem 512-blocks Free %Used Iused %Iused Mounted on
/dev/hd4 209715200 24745944 89% 1193733 30% /
/dev/hd2 12582912 2708632 79% 33947 11% /usr
/dev/hd9var 524288 267704 49% 895 3% /var
/dev/hd3 524288 131248 75% 1058 7% /tmp
/dev/fwdump 1048576 1047760 1% 4 1% /var/adm/ras/platform
/dev/hd1 524288 173800 67% 245 2% /home
/proc - - - - - /proc
/dev/hd10opt 8912896 6593016 27% 5876 1% /opt
/dev/fslv01 1254096896 296896640 77% 66766 1% /oradata
/dev/vx/dsk/dg2/app1 503296000 459251862 9% 2532 1% /app1
/dev/vx/dsk/dg2/data1 2205465696 662361536 70% 105922 2% /data1
/***********************************/
/*************************************/
机器3:
Filesystem 512-blocks Free %Used Iused %Iused Mounted on
/dev/hd4 209715200 201202392 5% 4549 1% /
/dev/hd2 9961472 749736 93% 30383 26% /usr
/dev/hd9var 6291456 1939560 70% 94878 31% /var
/dev/hd3 4194304 3083944 27% 222 1% /tmp
/dev/fwdump 1048576 1047760 1% 4 1% /var/adm/ras/platform
/dev/hd1 524288 310640 41% 1165 4% /home
/proc - - - - - /proc
/dev/hd10opt 2097152 136384 94% 5740 26% /opt
/dev/vx/dsk/fjcj/app 524288000 305641924 42% 3395535 15% /app
/dev/vx/dsk/fjcj/data 6479960064 1256161044 81% 23926583 23% /data
/*************************************/
三台机器,运行同样的语句,速度是递减的,机器3运行那个dd语句是最慢的,需要20多秒.
后来我测试了另一条dd语句:dd if=$1 of=$dp bs=1 skip=$((2048*i+20+${diff}*186)) count=186
这条语句在三台机器上的差别就没那么离谱了.想想应该是count值影响的.
请问下大家,有哪些因素会影响到dd的速度? |
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