Re: WAL segment question

Donald Fraser wrote:
> Our company has two sites, a master and a disaster recovery site.
> I am trying to assess whether data has been lost during a fail-over,
> due to the asynchronous method of transporting WAL file data between
> sites (we use DRBD).
>
> Disaster recovery node start-up log:
> user= pid=9907 timestamp=[2007-08-01 17:09:51 BST] tid= LOG: record
> with zero length at 0/7C62F52C
> user= pid=9907 timestamp=[2007-08-01 17:09:51 BST] tid= LOG: redo
> done at 0/7C62F4E8
>
> My question is: given the above WAL segment information, can I use it
> to decide whether information was lost in the master database site, at
> the point of failure, without starting the database up?
>
> Regards
> Donald Fraser.
DRBD is a synchronous method of transferring data - it's not
asynchronous. Assuming you are using Protocol C you should find that
both are always in sync. If you are using protocol B then things will
be in sync so long as the remote system didn't crash, and if you are
using Protocol A then things should be in sync as long as the local
system didn't crash.

--
Chander Ganesan
Open Technology Group, Inc.
One Copley Parkway, Suite 210
Morrisville, NC 27560
919-463-0999/866-229-3386
http://www.otg-nc.com