How to test the read and write speed of linux disk with dd command
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1. Familiarize yourself with two special devices:
(1) / dev/null: recycle bin, bottomless pit.
(2) / dev/zero: generates characters.
2. Test disk writing ability
The code is as follows:
Time dd if=/dev/zero of=/testw.dbf bs=4k count=100000
Because / dev//zero is a pseudo device, it only generates an empty character stream and does not generate IO for it, so IO is concentrated in of files and of files are only used for writing, so this command is equivalent to testing disk write ability. Adding oflag=direct at the end of the command skips the memory cache, and adding oflag=sync skips the hdd cache.
3. Test disk read ability
The code is as follows:
Time dd if=/dev/sdb of=/dev/null bs=4k
Because / dev/sdb is a physical partition, reading it will result that IO,/dev/null is a pseudo device, which is equivalent to a black hole, and of to this device will not generate IO, so the IO of this command only occurs on / dev/sdb, which is also equivalent to testing the read ability of the disk. (Ctrl+c terminates the test)
4. Test the ability to read and write at the same time
The code is as follows:
Time dd if=/dev/sdb of=/testrw.dbf bs=4k
Under this command, one is the physical partition and the other is the actual file, and IO is generated for both reading and writing to them (read to / dev/sdb and write to / testrw.dbf). Assuming they are all on the same disk, this command is equivalent to testing the disk's read and write ability at the same time.
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