Continuent To Bring Open Source DB Replication To the Oracle World 83
Robert Hodges, CTO of Continuent, has an interesting blog entry about a new approach to database replication that they are undertaking. The new approach aims to provide easier access to replication for low-end Oracle users in addition to the alpha offering they already have for MySQL. "It's not a coincidence that we chose to implement MySQL and Oracle replication at the same time. MySQL has revolutionized the simplicity and accessibility of databases in general and replication in particular. For example, MySQL users have created cost-effective read scaling solutions using master/slave replication for years. MySQL replication is not free of problems, but there is no question MySQL AB helped by the community got a lot of the basics really right. On the other hand, Oracle replication products offer state-of-the-art solutions for availability, heterogeneous replication, application upgrade, and other problems, albeit for high-end users. For example, Oracle Streams and Golden Gate TDM offer very advanced solutions to the problem of data migration with minimal downtime. The big problem with these solutions is not capabilities but administrative complexity and cost."
Re:MySQL + Oracle = MyOracle (Score:4, Interesting)
MySQL is better for small Databases, Oracle is better for Big ones.
(Small Databases consist of Millions of records, Big ones Billions) Installing Oracle for average Joe company is overkill, and huge overhead. That is why a lot of Oracle shops switched to Microsoft SQL, and MySQL.
It would be nice to have a lot of the features of Oracle with ability to manage small databases.
Re:MySQL + Oracle = MyOracle (Score:4, Interesting)
Oracle Express - 0$
Yes - if you want more features, Oracle is expensive. Although that cost includes support. But that has nothing to do with his statement of a hybrid - unless you are saying the only thing that will be merged is cost.
Re:Targeted to smaller shops. (Score:4, Interesting)
I am sure there is a huge market for Replication. Small Databases need to be rock solid too. Just because you may have a lot of data doesn't mean it isn't important or mission critical. Paying an extra $2000 for a server for a fail over is well worth the cost of your only SQL (Any Brand) server being down for a few hours to days.
Re:Looks a bit slashvertisment-y (Score:5, Interesting)
As always, the answer is 'It depends' (Score:4, Interesting)
It depends on what type of replication one needs. The simplest means of Oracle replication is to create another database somewhere else and simply copy the logs over and apply them. We have done that for years for one simple reason ... for databases that don't require 5 nines service, I don't want an 'up-to-date' copy.
A major cause of database failures in my experience has been due to programmer or administrator error (i.e. program bug or someone typing truncate table wrong.) Creating scripts to copy the logs to another server as soon as they are created, and applying them after they are a few hours old, we maintain an environment where it only takes a few minutes to switch over and prevent the 'uh-oh' moments from corrupting both databases.
We have found that the decision to switch over to a remote database takes time. No one wants to do it because then we have to copy that whole database back to the primary site eventually, and that takes a lot of effort and time. When we have a failure, someone is tasked at getting the remote database ready while the discussions are held whether or not to fix or fail-over.
One benefit of this has been that when we have 'uh-oh' moments, the old data is still available and we can correct it, sometimes without the end-users even being impacted.
So .. for all of you database admins out there, replication is possible without the fancy software *IF* you can write scripts, create a somewhat simple system to repoint to the new one (i.e. DNS), and can live with a few minutes of downtime a couple of times a year.
Re:MySQL + Oracle = MyOracle (Score:3, Interesting)
What's the long term cost of having a database run by somebody who doesn't know how to run a database?
If nothing will ever be done that requires dba knowledge - then a ton of products will work and Oracle Express falls into that category - with SQL Server Express in a similar boat. (Though SQL Server is limited to a single OS.)
I think people really overestimate what it takes to get Oracle installed and running. It's not that hard to do and their are vast resources available to help get one up and going. The learning curve comes as one starts to take advantage of features that aren't all that complicated but extremely powerful.
I've seen people used to working on Oracle come to me with problems they have with a MySQL database they built for something. They love it until they have a problem. Then they come ask me to fix it, like we fix their mistakes they make in the Oracle database. Problem is, we can't because they haven't done the work to make it possible.
Like any other product - MySQL is only as good as the people who have installed it and set it up.
Re:As always, the answer is 'It depends' (Score:4, Interesting)
No machine is 'up-to-date' as there is no such thing as instantaneous data transfers *unless* data is applied and committed to both machines at the same time. This is very costly outside of a local area. Before Oracle had replication services, we used this and were able to keep the remote machine (which was 2,000 miles away) within 5 minutes of the primary 95% of the time. It dawned on us one day how dangerous this was and changed it to not apply the logs for 60 minutes since it would only take us about 10 minutes to catch it up and switch it from stand-by, longer than it would take to decide to fail over and change DNS.
I did not mean to imply this was the best solution for replication, only that if someone is using replication software for this type of purpose, i.e. disaster recovery, then this is a perfectly acceptable solution that probably will work for any database and does not require additional licenses *except* for the remote machine. Oracle allowed us to run the remote machine this way without a license since we did not use it in a production capacity.
A backup solution??? I guess it is a backup of the primary, but many replicate machines are this way since 2-way replication difficulties often limits the usability of the remote server beyond read-only access. The data is never used to 'restore' the original machine, it is an exact, fully usable copy. If the primary machine crashed, the choices are to restore from tape, or make the remote machine the primary. The remote machine can serve as the production server for as long as is necessary. To restore the primary machine after the remote server has been used for an extended period, a backup of the remote has to be taken and applied to the primary. This can take a few days as the amount of data needed to be transferred is very high. A backup is taken to tape, overnighted, applied, and then additional log files are applied until the two are in sync and a point is reached where a controlled fail-back can occur.
In fact, at one facility, we 'swapped' machines every 30 days to make sure they would function if one failed.
Re:Looks a bit slashvertisment-y (Score:2, Interesting)
We replicate from Oracle to MySQL using redo-logs and a 143 line perl script. This has worked for about the last year, although there is a 15 minute delay in Oracle 9i, as there is no easy way to query online redo logs. All that changes when our data warehouse goes up to 10g, at that point we will get real time replication.
The MySQL database is only 250gig, around 2.2 billion records, used for all our websites (read-only), while all update systems hit Oracle, the updates are fed to a single MySQL master, which then uses MySQL replication to replicate to the web farm. No need to validate data on the MySQL servers, as the Oracle box has already done that.
Re:MySQL + Oracle = MyOracle (Score:3, Interesting)
Anyone can go to Oracle's web site and download the enterprise version of the database and install it. There is no activation or key necessary. Oracle can't do anything to your database.
As you say - you are in violation of the license if you use it that. Also - when you pay it isn't just to license the software. It is for support. And without a current support contract, you can't call oracle support or log in to metalink for support, downloading patches, etc.
More companies should handle these things the way that Oracle does.