On Fri, Feb 03, 2017 at 12:31:49AM +0100, Gianluca Cecchi wrote:
> On Thu, Feb 2, 2017 at 10:53 PM, Benjamin Marzinski
> <[1]bmarz...@redhat.com> wrote:
>
> > > I'm trying to mitigate inserting a timeout for my SAN devices but
> I'm not
> > > sure of its effectiveness as CentOS 7 behavior of "multipathd -k"
> and then
> > > "show config" seems different from CentOS 6.x
> > > In fact my attempt for multipath.conf is this
>
> There was a significant change in how multipath deals with merging
> device configurations between RHEL6 and RHEL7. The short answer is, as
> long as you copy the entire existing configuration, and just change what
> you want changed (like you did), you can ignore the change. Also,
> multipath doesn't care if you quote numbers.
>
> If you want to verify that no_path_retry is being set as intented, you
> can run:
>
> # multipath -r -v3 | grep no_path_retry
>
> Hi Benjamin,
> thank you very much for the explanations, especially the long one ;-)
> I tried and confirmed that I has no_path_retry = 4 as expected
> The regex matching is only for merge, correct?
No. Both RHEL6 and RHEL7 use regex matching to determine which
device configuration to use with your device, otherwise
product "^1814"
would never match any device, since there is no array with a literal
product string of "^1814". RHEL7 also uses the same regex matching to
determine which builtin device configuration a user-supplied device
configuration should modify. RHEL6 uses string matching for this.
> So in your example if in RH EL 7 I put this
> device {
> vendor "IBM"
> product "^1814"
> no_path_retry 12
> }
> It would not match for merging, but it would match for applying to my
> device (because it is put at the end of config read backwards).
correct. The confusing point is that in the merging case, "^1814" in
the user-supplied configuration is being treaded as a string that needs
to regex match the regular expression "^1814" in the builtin
configuration. These don't match. For matching the device configuration
to the device, "^1814" in the user-supplied configuration is being
treated as a regular expression that needs to regex match the actual
product string of the device.
> And it would apply only the no_path_retry setting, while all other ones
> would not be picked from builtin configuration for device, but from
> defaults in general.
> So for example it would set path_checker not this way:
> path_checker "rdac"
> but this way:
> path_checker "directio"
> that is default..
> correct?
exactly.
-Ben
> References
>
> Visible links
> 1. mailto:bmarz...@redhat.com
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