Re: Fault Tolerant Postgresql (two machines, two postmasters, one disk array)

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On 05/17/07 09:35, Andrew Sullivan wrote:
[snip]
>
> The problems come when you get a false detection of machine failure.
> Consider a case, for instance, where the machine A gets overloaded,
> goes into swap madness, or has a billion runaway processes that cause
> it to stagger.  In this case, A might not respond in time on the
> heartbeat monitor, and then the standby machine B thinks A has
> failed.  But A doesn't know that, of course, because it is working as
> hard as it can just to stay up.  Now, if B mounts the disk and starts
> the postmaster, but doesn't have a way to make _sure_ tha A is
> completely disconnected from the disk, then it's entirely possible A
> will flush buffers out to the still-mounted data area.  Poof!
> Instant data corruption.

Aren't there PCI heartbeat cards that are independent of the load on
the host machine?

- --
Ron Johnson, Jr.
Jefferson LA  USA

Give a man a fish, and he eats for a day.
Hit him with a fish, and he goes away for good!

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