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Expected behaviour of "on-io-error pass_on"

 

 

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arne.redlich at googlemail

Jul 25, 2012, 7:11 AM

Post #1 of 3 (711 views)
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Expected behaviour of "on-io-error pass_on"

Hi,

There seems to be a disagreement between the documentation and the
actual code wrt the "pass_on" I/O error handling strategy in drbd 8.4.

Quoth http://www.drbd.org/users-guide/s-configure-io-error-behavior.html:
"2. pass_on This causes DRBD to report the I/O error to the upper
layers. On the primary node, it is reported to the mounted file
system. On the secondary node, it is ignored (because the secondary
has no upper layer to report to)."

The code however suggests that reads are redirected to the secondary
if the primary returned an error, and errors are not reported to the
upper layers unless the secondary cannot satisfy the read request
either.

Bug in the code or in the documentation?

Thanks,
Arne
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lars.ellenberg at linbit

Jul 25, 2012, 12:41 PM

Post #2 of 3 (675 views)
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Re: Expected behaviour of "on-io-error pass_on" [In reply to]

On Wed, Jul 25, 2012 at 04:11:42PM +0200, Arne Redlich wrote:
> Hi,
>
> There seems to be a disagreement between the documentation and the
> actual code wrt the "pass_on" I/O error handling strategy in drbd 8.4.
>
> Quoth http://www.drbd.org/users-guide/s-configure-io-error-behavior.html:
> "2. pass_on This causes DRBD to report the I/O error to the upper
> layers. On the primary node, it is reported to the mounted file
> system. On the secondary node, it is ignored (because the secondary
> has no upper layer to report to)."
>
> The code however suggests that reads are redirected to the secondary
> if the primary returned an error, and errors are not reported to the
> upper layers unless the secondary cannot satisfy the read request
> either.
>
> Bug in the code or in the documentation?

Bug in user's guide, copied and recopied from old man pages.
See also
http://git.drbd.org/gitweb.cgi?p=drbd-8.3.git;a=commitdiff;h=9ef05ced
equivalent merge commit is in 8.4 as well.

The "passes error on to upper layers" was last describing the code
almost correctly for drbd 0.7, and for failed READs, only...

And that setting, even though "default" for much too long,
was not very useful back then already.

What is it you are trying to achive, that you even noticed this?

--
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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ff at mpexnet

Jul 26, 2012, 2:39 AM

Post #3 of 3 (674 views)
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Re: Expected behaviour of "on-io-error pass_on" [In reply to]

On 07/25/2012 09:41 PM, Lars Ellenberg wrote:
> On Wed, Jul 25, 2012 at 04:11:42PM +0200, Arne Redlich wrote:
>
> > Quoth http://www.drbd.org/users-guide/s-configure-io-error-behavior.html:
> > ...
>
> The "passes error on to upper layers" was last describing the code
> almost correctly for drbd 0.7, and for failed READs, only...

Quoth the dev'er, "Nevermore".

(Sorry, couldn't resist.)
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