![]() ![]() After cloning Linux partition, you can then check both partitions with: fdisk -l /dev/sdb1 /dev/sdc1. The above command tells dd to use /dev/sdb1 as input file and write it to output file /dev/sdc1. Let’s improve the previous line storing the block size in a variable called BLOCKSIZE: $ BLOCKSIZE=$(stat -c "%o" /tmp/inputfile.bin)įinally, we can use what we’ve just learned to write a small script to use dd with the block size the previous command found. Now clone a partition /dev/sdb1/ to /dev/sdc1 using the following dd command. If we use the parameter -c %o, stat will print only the block size. This example, for instance, will create a compressed image of a remote drive using SSH and save the resulting archive to your local machine: ssh username54.98.132.10 'dd if/dev/sda gzip -1 -' dd ofbackup. Use the dd command to measure server throughput (write speed): dd if/dev/zero of/tmp/test1. Stat accepts a parameter -c (or –format) that allows us to specify what information we want. dd ifsdadisk.img of/dev/sdb You can also perform both the create and copy operations in one command. Use dd command to monitor the reading and writing performance of a disk device: Open a shell prompt. calculate_best_bs.shįastest Block Size: 32768 3. We can limit the time it takes the script to run by adding or removing block size values, and by changing the timeout. The script has an array of block sizes we want to test, and also a timeout of 20 seconds. Also, we may want to modify the output file $OF so the script writes to the desired filesystem. dd will happily copy using the BS of whatever you want, and will copy a partial block (at the end). Note we need to run this script as a root, so it can drop the disk cache before each run. ![]() This will then fill gzip's buffer at sata or sas line rate strait from the drives buffer. ![]() Specifying a bs parameter that aligns with the disks buffer memory will get the most performance from the disk. Now clone a partition /dev/sdb1/ to /dev/sdc1 using the following dd command. If thenĮcho Fastest Block Size: $BEST_BLOCK_SIZE First you need to get DD's performance up. * - All files in the current directory.Unlike other options for GNU parallel ::: is placed after the command and before the arguments. Use arguments from the command line as input source instead of stdin (standard input).::: - Tell parallel to use the next argument as input instead of stdin.Or use cat on Linux I found cat to be as fast as dd with the optimal block size when a single disk was involved (I dont know if that holds for OSX as well). Use a higher block size (on a hunch Id say a few MB) for good performance. Take note of that number and then type in another terminal window kill -USR1 4112 sleep 1 This will give me the time, seconds elapsed since it began and how much is has copied. dd with a tiny block size like 512 bytes is likely to be a lot slower than your disks maximum throughput. If you have GNU Parallel installed you can do this: parallel -j10 cp will be appended to the command line. You can see the process ID by typing ps -e and looking for dd or just ps -egrep dd and looking at the number in the front. ![]()
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