Testing User Disk Speed for Read and Write

Jovan S Hernandez
1 min readApr 13, 2017

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For those of you comfortable in Terminal or CLI, here is a very good tool to test a users disk speed for reading and writing. I usually use BlackMagic Disk Speed Test which you can download from the app store, but you can run this terminal command on the users computer instead. The test times how long it takes to read or write a 1GB file.

#Disk Speed Test Write: 
time dd if=/dev/zero bs=1024k of=tstfile count=1024
#Disk Speed Test Read:
dd if=tstfile bs=1024k of=/dev/null count=1024

You will receive an output that resembles the data below:

Write:
time dd if=/dev/zero bs=1024k of=tstfile count=1024
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 2.342969 secs (458282568 bytes/sec)
Read:
dd if=tstfile bs=1024k of=/dev/null count=1024
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 2.085392 secs (514887285 bytes/sec)

Take the bottom line of your output and you can copy paste the ratio to get an actual human readable speed. 514887285 bytes/sec = 514.88MB/s.

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