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VPS performance test tool 3: dd hard disk read/write command

Lao Zuo shares the third Linux today VPS performance test Tool to test the read/write speed of the hard disk with dd command. First, explain what the dd command is. dd is one of the useful commands for Linux/UNIX. It is used to specify the size of a block to copy, and to specify the conversion when copying. I can't say anything else. I don't engage in scientific research, as long as I can use it directly. I need to go to the encyclopedia to learn more about the dd command.

Two common test commands:

dd if=/dev/zero of=test bs=64k count=4k oflag=dsync
dd if=/dev/zero of=test bs=8k count=256k conv=fdatasync

The difference between conv=fdatasync and oflag=dsync is that the sync function only queues all modified block buffers into the write queue, and then returns. It does not wait for the end of the actual disk write operation. The fsync function only works on a single file specified by the file descriptor filedes, and waits for the end of the disk write operation before returning. So the speed of fdatasync is better than that of dsync.

 Sugarhost VPS dd disk write performance


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