Re: [Xen-users] Databases and Virtualisation Basic Question

[Michael Schmidt <michael.schmidt@xxxxxxxxxx>]

Hi Geoffrey,

Am 13.05.10 00:31, schrieb Geoff Hoyle:

We are looking to use virtualisation on a new project to help with deployment etc.

One of the servers will be database server, specifically the RDBMS will be PostgreSQL.

Therefore on that server will be the host Linux OS with a guest Linux OS running on Xen. The guest OS is the one with the database.

Just one personal note here: I am running a lot of virtual SQL servers (MySQL and PGSQL) on each xen-server.
The sum of performance of this many short SQL machines is a lot higher than one big database server. So it sound like a good idea :)

 

My question is

 

If the database is running on a guest OS with its own disk space etc and we then wish to deploy and run a newer image due to a software change or something what happens to the data in the database on the older image? Is this lost? 

How can the new image pick up the existing data? Am I having a fundamental misunderstanding?

 

You want to update the OS without loosing your SQL data, right?
So use one virtual-disk for your linux installation and another virtual disk for your SQL data (and mount this disk eg. to /var/lib/postgresql/).
Then you can touch your virtual OS disk for os upgrades and so on, and ensure, that your sql data keeps untouched.

Greetings
- Michael Schmidt

 

Thanks in advance for your responses.
 

Geoffrey Hoyle BSc MBCS

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