Re: [9.0] hot standby plus streaming replication

Gabriele Bartolini ha scritto:

Ciao Michele,

Ciao ;)

both server (master and standby) need a common directory where
read

and write the wal files?

Not necessarily. You can use for instance scp to ship the WAL file
from the master to the standby using the network.

Thanks for the explain, but...
- why in my tests, _whitout_ common direcotory, master and slave keep in
sync also if I shutdown slave, add (in my last tests) something about
100k record (although little ones) on the master and then after woke up
the slave in about 2/3 seconds I have all the dbs in sync? It's just
luck or there are something that I don't understand?
- If I have to copy (scp / rsync / etc...) the files, which interval I
have to follow? And also, when the slave will read these files? There
are something like inotify or I have to say to slave "my friend, there
are updates from master. Keep in sync!"

Just another question about replication: there is the possibility
to

build a sync between a 32 and a 64 bit (on linux)?

As stated in the documentation
(http://www.postgresql.org/docs/9.0/static/warm-standby.html), the
hardware architecture must be the same.

If I read before this page, I spared a lot of tries!

Hope this helps.

Ciao, Gabriele

Thanks a lot,
Michele

P.s. Glad to see that also in Italy there are PostgreSQL guru ;)

P.s. Glad to see that also in Italy there are PostgreSQL guru ;)

Glad to see that more people are using Indian words (Guru) :)
http://en.wikipedia.org/wiki/Guru

Regards,
Jayadevan

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On Fri, Oct 1, 2010 at 4:02 PM, Michele Petrazzo - Unipex
<michele.petrazzo@unipex.it> wrote:

- why in my tests, _whitout_ common direcotory, master and slave keep in
sync also if I shutdown slave, add (in my last tests) something about
100k record (although little ones) on the master and then after woke up
the slave in about 2/3 seconds I have all the dbs in sync?

Because the master had the WAL files containing that 100k record in its
pg_xlog directory. If those WAL files were unfortunately removed from
the master before you started the standby, the standby would not have
been in sync with the master.

You can specify how many WAL files you'd keep in the master by using
wal_keep_segments parameter.
http://developer.postgresql.org/pgdocs/postgres/runtime-config-wal.html#RUNTIME-CONFIG-REPLICATION

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

Fujii Masao ha scritto:

On Fri, Oct 1, 2010 at 4:02 PM, Michele Petrazzo - Unipex
<michele.petrazzo@unipex.it> wrote:

- why in my tests, _whitout_ common direcotory, master and slave
keep in sync also if I shutdown slave, add (in my last tests)
something about 100k record (although little ones) on the master
and then after woke up the slave in about 2/3 seconds I have all
the dbs in sync?

Because the master had the WAL files containing that 100k record in
its pg_xlog directory. If those WAL files were unfortunately removed
from the master before you started the standby, the standby would
not have been in sync with the master.

This was the explain that I was looking for!
Do you know if there is a talk or a "best practice" about keep in sync a
master/slave couple without a shared directory? Something that talk
about the number of a typical data that can be keep in sync.
Can be very useful and more simple to maintain an installation without a
shared than a one with it and I think that more users will be happy with!

You can specify how many WAL files you'd keep in the master by using
wal_keep_segments parameter.
http://developer.postgresql.org/pgdocs/postgres/runtime-config-wal.html#RUNTIME-CONFIG-REPLICATION

Seen!
Thanks a lot,
Michele