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I have a disk attached to my RHEL client, where I have to run IO continuously for very long time. But I have a storage limitations, where disk size is only 300GB.

Usually I use Vdbench Tool to run IO. There is one existing vdbench running in the background and I came to know that we can not create two instances of vdbench to run IO.( correct me if I am wrong)

As I need to fill my disk, tried dd command.

dd if=/dev/zero of=zeros bs=1M

This will literally fill the hard drive until disk is out of disk space. Thens stops.

My question here, how to run dd continuously for infinite time, even after disk is full ? Can dd overwrite the data once disk is full and run IO for ever ?

Any other tool to run io, which serves the purpose ? Please suggest.

Thanks in advance.

Subhash
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  • Just delete the file and start over? – James Z Apr 02 '18 at 07:07
  • @JamesZ, good idea, but I need a continuous uninterrupted IO to run on the disk. And I have 100+ such disks, where continuous IO should be running. – Subhash Apr 02 '18 at 07:13
  • What exactly are you trying to test? `dd` is usually a pretty poor substitute for a true IO benchmarking program as it merely streams chunks of data. So unless your system's actual IO pattern is to stream large files, a `dd` test will usually be meaningless. – Andrew Henle Apr 02 '18 at 17:27

2 Answers2

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Like you said, this will fill the disk until it runs out of space. There is nothing dd can do after that, so it will terminate with an error.

You could write an enless loop, like Subhash suggested: 

while true
do
    dd if=/dev/zero of=zeros bs=1M
    rm zeros
    echo "Restarting..."
done
phisch
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0

Vdbench 'seek=seq' will do just fine.When it reaches the end it will just start at the beginning again. And no, there is no reason why you can't run multiple instances of Vdbench. (Years ago there was a maximum of eight instances).

Henk
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