Re: Oracle and DRBD - a real HA alternative?
- From: Mark Brinsmead <pythianbrinsmead@xxxxxxxxx>
- To: uwe@xxxxxxxxxxxx
- Date: Thu, 21 Jan 2010 20:49:22 -0700
I have looked at this before, as sort of a "thought experiment".
You could use DRDB to replicate *all* of the database storage -- and maybe
the Oracle software, OS, etc -- and get a pretty decent failover
capability. (Oh -- actually, you can't mirror the OS with DRDB, can you?)
But you could be looking at a lot of network bandwidth, and possible impair
the performance of the "primary" database.
If you can afford the database licenses, do this:
"Clone" your database onto the second server, and start it up as a standby.
Transport archivelogs, and apply them. Use DRDB to mirror ONLY the online
redologs; this gives you what you need for complete recovery of the standby.
This method requires a lot less network bandwidth that mirroring the entire
database with DRDB, and avoids (most) of the risk of impairing performance
on the primary database.
You may also need to also use DRDB to mirror the archived redologs to avoid
race conditions that might prevent to some failovers from succeeding. I
haven't really worked out that part of the experiment yet.
Now, *why* would you do this, when you could have used Data Guard instead?
Well, if you *have* Data Guard, you *should* use it. But there is no Data
Guard with Standard Edition.
Your original method has its own advantages, though. You don't need to
license the standby database server until you failover. (although you *will
* be limited in the number of times you start the Oracle software --
presumably for failover tests -- before you *do* have to license the standby
server.)
Will my idea work? Dunno. Never tried it. But it should.
2010/1/21 Uwe Küchler <uwe@xxxxxxxxxxxx>
> Dear fellow oracle-l'ers,
>
> recently I stumbled over a high availability (HA) concept for an Oracle
> DB server that involves DRBD, at least for the OS and storage part. The
> concept was presented by an outsourced server provider to their customer.
>
> What made me wonder is, that the customer wants HA for the _database_
> and not only for the storage. As far as I know, DRBD only covers the the
> OS and storage level and not the Oracle Server itself - that's why I'd
> like to suggest using Data Guard or maybe even RAC.
>
> Does anyone here have practical experience in running DRBD with Oracle
> Server? Is it possible to create anything near to Data Guard
> functionality with it? How would you implement a transparent application
> failover? What about split-brain situations?
>
> Lots of questions, I know. But maybe you can show me a few good pointers
> to tell me "it's possible at all" or "Oracle Server failover isn't
> possible with DRBD".
>
> Have a good day!
> Uwe
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
--
Cheers,
-- Mark Brinsmead
Senior DBA,
The Pythian Group
http://www.pythian.com/blogs
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