Sounds fine, though note that we don't want ob1 itself to do this as
it inevitably adds overhead that translates into latency. Instead, we
want that functionality to be in a separate component for those people
who want to use it.
We did talk on a telecon earlier this week about the need to refactor
the PML so that all these various PML components don't have to keep
tracking what is done in ob1 - bit of a pain. Nothing has been done
yet, but hopefully at some point we'll address this issue.
On Apr 16, 2009, at 2:33 AM, Sylvain Jeaugey wrote:
Well, if reviving means making device failover work, then yes, in a
way we revived it ;)
We are currently making mostly experiments to figure out how to have
device failover working. No big fixes for now, and that's why we are
posting here before going further.
From what I understand, Rolf's work seems very close to what we
want to do
and we'd better work with him on making ob1 able to do device
failover rather than trying to work on dr.
This sound good to me : there is no reason why ob1 couldn't
invalidate a device (e.g. if we send a signal). However, replaying
lost sends still seems to be needed if we want to be able to handle
a network failure. Clearly, ob1 doesn't support this yet.
Thanks a lot for your advices, we will continue to think about it
and come back to you.
Sylvain
On Wed, 15 Apr 2009, Ralph Castain wrote:
Last anyone knew, the dr pml was dead - way out of date and
unmaintained. I gather that you folks have revived it and sync'd it
back up to the current ob1 module?
I don't think anyone really cares what is done with the dr module
itself. There are others working on failover modules, and there is
a new separate checksum module that just aborts if it detects an
error.
So I would guess you are welcome to do whatever you want to it. I
suspect the others working on failover may speak up here too.
On Apr 15, 2009, at 6:47 AM, Mouhamed Gueye wrote:
Hi all,
We are currently working on the dr pml component and specifically
on device failover. The failover mecanism seems to work fine on
different components, but if we want to do it on different modules
of the same component - say 2 Infiniband rails - the code seems to
be broken.
Actually, when the first openib module fails, the progress
function of the openib component is deregistered and progress is
no longer made on any openib module. We managed to circumvent this
by keeping the progress function as long as an openib module might
be using it and it seems to work fine.
So I have a few questions :
1. Is there already work in progress to support multi-module
failover on the dr pml ?
2. Do you think this is the correct way to handle multi-module
failover ?
Also, the fact that the "dr" component includes many things like
checksuming bothers us a bit (we'd like to lower performance
overhead as far as possible when including device failover). So,
3. Do you plan to fork this component to a "df (device failover)
only" one ? (we would like to, but maybe this is not the right way
to go)
That's all for now,
Mouhamed
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