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Re: Question about IO workload via NBD

Hi All,

After specifying sync and flush error correctly, this issue seems to
be fixed. But we still encounter IO error with FIO running on NBD that
seems to cause by disconnection

The error is like
fio: io_u error on file /dev/nbd0: Input/output error: write
offset=xxxx, buflen=xxxx

I already specified 'persist' option while launching the nbd-client.
Is there any other things I could do on the NBD side or the FIO side
to prevent this error?

Any help is appreciated.

Thank you!
Best wishes,

On Tue, Sep 3, 2019 at 2:47 PM Taylor Yang <taylor4869@gmail.com> wrote:
> Hi Richard,
> The command I use is like `fio --name=xxx --rw=randread --output=xxx
> --direct=1 --ioengine=libaio --bs=16k --iodepth=4 --filename=/dev/nbd0
> --size=1024Mb` and I setup both nbd client and nbd server on two
> different hosts. The FIO job is executed on the nbd client side after
> the connection between the nbd client and server being setup. I think
> it is because nbd server uses the buffer cache but I also tried to
> specify the `sync` option in the config file and it still behaves the
> same way.
> Any suggestion is appreciated.
> Thank you!
> Best wishes,
> Taylor
> On Mon, Sep 2, 2019 at 2:48 PM Richard W.M. Jones <rjones@redhat.com> wrote:
> >
> > On Fri, Aug 30, 2019 at 05:23:44PM -0700, Taylor Yang wrote:
> > > Hi,
> > >
> > > I worked on driving IO workload using FIO to a device via NBD. There
> > > seems to be some delay on the IO being shown on the original device
> > > after the FIO workload completed on the NBD. Is there a delay on how
> > > long the IO would be acknowledged on the original device? Is there any
> > > logging information I could get to troubleshoot this issue?
> > >
> > > Thank you so much for your help in advance.
> >
> > What's the fio command line / configuration file?  Are you
> > using the NBD engine or a filesystem?
> >
> > Rich.
> >
> > --
> > Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
> > Read my programming and virtualization blog: http://rwmj.wordpress.com
> > virt-top is 'top' for virtual machines.  Tiny program with many
> > powerful monitoring features, net stats, disk stats, logging, etc.
> > http://people.redhat.com/~rjones/virt-top

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