Dale Ghent wrote:
On Sep 13, 2006, at 12:32 PM, Eric Schrock wrote:
Storing the hostid as a last-ditch check for administrative error is a
reasonable RFE - just one that we haven't yet gotten around to.
Claiming that it will solve the clustering problem oversimplifies the
problem and will lead to people who think they have a 'safe' homegrown
failover when in reality the right sequence of actions will irrevocably
corrupt their data.
HostID is handy, but it'll only tell you who MIGHT or MIGHT NOT have
control of the pool.
Such an RFE would even more worthwhile if it included something such as
a time stamp. This time stamp (or similar time-oriented signature) would
be updated regularly (bases on some internal ZFS event). If this stamp
goes for an arbitrary length of time without being updated, another host
in the cluster could force import it on the assumption that the original
host is no longer able to communicate to the zpool.
That might be acceptable in some environments but that is going to cause
disks to spin up. That will be very unacceptable in a laptop and
maybe even in some energy conscious data centres.
What you are proposing sounds a lot like a cluster hear beat which IMO
really should not be implemented by writing to disks.
--
Darren J Moffat
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