DD command test Drive read and write speed

1. DD Command Brief:

if= input file, of= output file, ibs= bytes read at a time, obs= write bytes at a time, bs= set the number of bytes written at one time, skip= skipped BS number, count= copy block number

2. Using/dev/null and/dev/zero

　　1. Treat/dev/null as a "black hole", which is equivalent to a write-only file, and all content written to it will be lost forever

2./dev/zero is a pseudo-file, but it actually produces a continuous stream of NULL

3. Test drive Read and write speed

# # cut into the U-disk directory, test write speed
# dd If=/dev/zero of=./largefile bs=8k count=10000
10000+0 records in 
 10000+ 0 records out 
 81920000  bytes  (82 Mb Copied, 11.0626 s , 7.4 Mb/ s 
 
 # # Test read speed (clear cache) 
 # sudo sh-c "Sync && echo 3 >/proc/sys/vm/drop_caches"  & nbsp;    
 # dd If=./largefile of=/dev/null bs=8k 
 8000+0 Records in 
 8000+0 records out 
 65536000 Bytes (MB) copied, 2.90366 s, 22.6 mb/s 
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DD command to test disk read and write speed