Re: db replication and errors - Mailing list pgsql-general

Thanx for the pointers, Richard.

>> If the async feature is used on the primary, shud we
>> copy on the xlog and clog files onto the backup as
>> well?
>
>
> What is the "async feature"?

I meant fsync.
I meant to ask, if FSYNC is enabled, is all pending data written onto
the disk?

>
>> As of now, we shut down postmaster, on the Primary
>> whenever the standby boots up, and then copy all the above said files,
>> from the primary to the standby.
>>
>> Duz this ensure, all data is written onto the disk b4
>> postmaster shut downs?
>
>
> Provided the postmaster shuts down cleanly, and you've synced to disk
> then all should be OK.

Wot decides this "sync" n how do i check it?

>> Quite a few times, I have encountered errors, like, xlogflush is not
>> satisfied,
>> bogus attribute number for <some num , eg. -2>,  catalog is missing,
>> cache lookup failed.
>
>
> One of 4 things could be at fault:
>  1. Files aren't being sync'ed to disk
>  2. You aren't copying the right files
>  3. The versions of PG don't match
>  4. The platforms you are running on are different (e.g. Sun-Sparc vs
> x86)

The latter two are not the case, I use Redhat 9 on all the machines,
with PG VERSION 7.3
The former two, yes, I agree, cud be the cause of problems.

I would like to know, where to look on such errors.eg for cache lookup
failure, wot triggers that??how do i get abt tracking down the issue?

>
> It might be worth looking at "slony" to run a replication setup,
> rather than copying files.

Did think of slony previously. But slony has the limitation of not being
able to replicate large objects, rite?
How large are these large objects supposed to be?
Run-time replication is not an issue, as I have other mechanisms for
that, which are part of this server, and they work fine.
The only problem I am facing now, is of the case when the standby is
booting up. I have to ensure an absolutely correct copying of files.

I want to know how do i go about diagnosing problems, if and when they
arise.
I have come across pg_filedump. But cant really make out much frm the
output that pg_filedump produces.

A long way to go... I agree.



--

Benjamin Jacob.

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