Alternative replication method.
Has anyone used PostgreSQL with Drbd
(http://www.complang.tuwien.ac.at/reisner/drbd/)?
They claim it works with PostgreSQL. Do the PostgreSQL hackers forsee
any issues with this type of replication method?
Do you think this method (combined with some other HA utilities) could
work well as a "hot-spare" database server?
--
Best Regards,
Mike Benoit
NetNation Communications Inc.
Systems Engineer
Tel: 604-684-6892 or 888-983-6600
---------------------------------------
Disclaimer: Opinions expressed here are my own and not
necessarily those of my employer
I haven't used this. It would probably work, but there's also another
way just using plain SCSI. You can attach both your main machine and a
hot standby to an external RAID array. When the main machine goes down,
just mount the RAID array yourself. However, you should also install a
serial power switch so that you can kill the other server dead to prevent
possible damage.
Jon
On 24 Jun 2003, Mike Benoit wrote:
Show quoted text
Has anyone used PostgreSQL with Drbd
(http://www.complang.tuwien.ac.at/reisner/drbd/)?They claim it works with PostgreSQL. Do the PostgreSQL hackers forsee
any issues with this type of replication method?Do you think this method (combined with some other HA utilities) could
work well as a "hot-spare" database server?--
Best Regards,Mike Benoit
NetNation Communications Inc.
Systems Engineer
Tel: 604-684-6892 or 888-983-6600
---------------------------------------Disclaimer: Opinions expressed here are my own and not
necessarily those of my employer---------------------------(end of broadcast)---------------------------
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Mike Benoit <mikeb@netnation.com> writes:
Has anyone used PostgreSQL with Drbd
(http://www.complang.tuwien.ac.at/reisner/drbd/)?
Does it guarantee preservation of write ordering?
regards, tom lane
According to section 5 in this:
http://www.complang.tuwien.ac.at/reisner/drbd/publications/drbd_paper_for_LK7.pdf
it looks like it does guarantee write order.
<snip>
5 Write ordering
Some file systems require that certain blocks hit the media in a
determined order, for example a JFS
needs to write a transaction (the commit record must be last) into the
journal before it does any updates
to the home locations.
It does this by postponing the home location updates until it knows that
the writes to the journal are
on stable storage. (This is done with wait_on_buffer() and/or
buffer_uptodate())
From the DRBD's point of view the question is, which blocks might be
reordered when writing to the
secondary's disk.
To ensure exactly the same write order as on the primary, we must use
the following scheme:
1. Get a block from the network and put it onto the buffer cache.
2. Write that buffer and wait for IO completion.
3. Continue with 1.
...
</snip>
On Wed, 2003-06-25 at 07:44, Tom Lane wrote:
Mike Benoit <mikeb@netnation.com> writes:
Has anyone used PostgreSQL with Drbd
(http://www.complang.tuwien.ac.at/reisner/drbd/)?Does it guarantee preservation of write ordering?
regards, tom lane
--
Best Regards,
Mike Benoit
NetNation Communications Inc.
Systems Engineer
Tel: 604-684-6892 or 888-983-6600
---------------------------------------
Disclaimer: Opinions expressed here are my own and not
necessarily those of my employer