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On 03/10, Rikimaru Honjo wrote:
> Hello Gorka,
>
> On 2017/10/02 20:37, Gorka Eguileor wrote:
> > On 02/10, Rikimaru Honjo wrote:
> > > Hello,
> > >
> > > I'd like to discuss about the following bug of os-brick.
> > >
> > > * os-brick's iscsi initiator unexpectedly reverts node.startup from "automatic" to "manual".
> > >    https://bugs.launchpad.net/os-brick/+bug/1670237
> > >
> > > The important point of this bug is:
> > >
> > > When os-brick initializes iscsi connections:
> > > 1. os-brick will run "iscsiadm -m discovery" command if we use iscsi multipath.
> >
> > This only happens with a small number of cinder drivers, since most
> > drivers try to avoid the discovery path due to the number of
> > disadvantages it presents for a reliable deployment.  The most notorious
> > issue is that the path to the discovery portal on the attaching node is
> > down you cannot attach the volume no matter how many of the other paths
> > are up.
> >
> >
> >
> > > 2. os-brick will update node.startup values to "automatic" if we use iscsi.
> > > 3. "iscsiadm -m discovery" command will recreate iscsi node repositories.[1]
> > >     As a result, node.startup values of already attached volumes will be revert
> > >     to default(=manual).
> > >
> > > Gorka Eguileor and I discussed how do I fix this bug[2].
> > > Our idea is this:
> > >
> > > 1. Confirm node.startup values of all the iscsi targets before running discovery.
> > > 2. Re-update node.startup values of all the iscsi targets after running discovery.
> > >
> > > But, I afraid that this operation will take a long time.
> > > I ran showing & updating node.startup values 100 times for researching.
> > > As a result, it took about 4 seconds.
> > > When I ran 200 times, it took about 8 seconds.
> > > I think this is a little long.
> > >
> > > If we use multipath and attach 25 volumes, 100 targets will be created.
> > > I think that updating 100 times is a possible use case.
> > >
> > > How do you think about it?
> > > Can I implement the above idea?
> > >
> >
> > The approach I proposed is on the review is valid, the flaw is in the
> > specific implementation, you are doing 100 request where 4 would
> > suffice.
> >
> > You don't need to do a request for each target-portal tuple, you only
> > need to do 1 request per portal, which reduces the number of calls to
> > iscsiadm from 100 to 4 in the case you mention.
> >
> > You can check all targets for an IP with:
> >    iscsiadm -m node -p IP
> >
> > This means that the performance hit from having 100 or 200 targets
> > should be negligible.
>
> I have one question.
>
> I can see node.startup values by 1 request per portal as you said.
>
> But, may I update values by 1 request per portal?
> Updating values has been done by 1 request per target until now.
> So I think my patch should update values in same way(=1 request per target).
>

If all the targets on the same portal had the original same value you
should just make a single call after the discovery that changes them
all, at least that would be my preference.



> > Cheers,
> > Gorka.
> >
> >
> >
> > > [1]This is correct behavior of iscsiadm.
> > >     https://github.com/open-iscsi/open-iscsi/issues/58#issuecomment-325528315
> > > [2]https://bugs.launchpad.net/os-brick/+bug/1670237
> > > --
> > > _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> > > Rikimaru Honjo
> > > E-mail:honjo.rikimaru at po.ntt-tx.co.jp
> > >
> > >
> > >
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