[dm-devel] mirroring: [patch 5 of 6] device failure tolerance
Jonathan E Brassow
jbrassow at redhat.com
Thu Jun 30 19:05:29 UTC 2005
On Jun 30, 2005, at 1:10 PM, Jonathan E Brassow wrote:
>
> On Jun 30, 2005, at 12:56 PM, Alasdair G Kergon wrote:
>
>> On Thu, Jun 30, 2005 at 11:38:28AM -0500, Kevin Corry wrote:
>>> Any time a target's table-format or status-format changes, we also
>>> need to
>>> increment that target's version number so user-space can figure out
>>> which
>>> format to expect.
>>
>> Indeed, but I don't want version numbers updating till we know what
>> sequence things will go upstream.
>>
>> BTW I've not seen a justification for breaking the existing format
>> here
>> yet as opposed to simply appending new data to the end of the status
>> line.
>>
>
> mirror_status first calls the log status function and then adds on to
> that. If we want to do what you are proposing, we would move the log
> status function _after_ the DMEMIT's for mirror and it would only
> print out a char for each log device indicating status. We would have
> to remember that STATUSTYPE_INFO and STATUSTYPE_TABLE would call the
> log status function at different place (one after it's own DMEMITs,
> the other before).
>
Perhaps like the attached patch.
I think the pvmove stuff is already busted. How does it handle mirrors
with more than 2 sides? (ok, so pvmove isn't broken, but code that
uses the same function to determine a mirrors status would be - lvs?)
If we are going to add code that must correctly handle the number of
mirror args, I think we could add code to properly handle the log args
at the same time. Then we have some (limited) flexibility in how
things are handled.
brassow
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