Copy tomcat and mysql from one Amazon EBS volume to another

Question

I launched an Amazon EC2 with Amazon Linux and Amazon-EBS as root volume. I also started tomcat7 and mysql 5.5 on this EBS volume.

Later I decided to change from Amazon Linux to Ubuntu. To do that I need to launch another Amazon EC2 instance with a new EBS root volume. Now I want to copy tomcat7 and mysql from older EBS volume to new one. I have tables and data in mysql which I don't want to loose and an application running on tomcat. How to go about it?

Answer 1

A couple of thoughts and suggestions.

First, if you are going to be having any kind of significant load on your database, running it on EBS-backed volume is probably not a great idea as EBS-backed storage is incredibly slow relative to the machine's local/ephemeral storage (/mnt). Now obviously you don't want DB data on ephemeral storage, so there is really nothing you can do about it if you want to run MySQL on EC2. So my suggestion would be to utilize an RDS instance for your DB if your infrastructure requirements allow for it.

Second, if this is a production application, you are undoubtedly going to have some down time as you make this transition. The question is whether you need to absolutely minimize the amount of downtime. If so, then you need to have an idea as to the size of your database. Is it going to take a long time to dump/load? If not, you could probably just get your new instance up and running, and tested on an older copy of your database and then just dump and load the current database at the time of cutover.

If it is a large database then perhaps you can turn on MySQL binary logging. Then make a dump of the database at a known binary log position. Then install this dump on your new instance. Then when ready to cutover, you can replay the binary logs on the new instance to bring it current. Similarly, you could just set up the DB on the new instance as a replica until the cutover, at which point you make it the master.

You may even consider just using rsync to sync the physical database files if you don't want to mess with binary logging, though this can be a problematic approach if you are not that familiar with dealing with the actual physical database files.

As far as your application goes, that should be much simpler to migrate assuming it is just a collection of files. I would not copy the Tomcat7 installation itself, but rather just install Tomcat on Ubuntu and then adjust the configuration to match current.

As far as the cutover itself goes, this should be pretty straightforward and would vary in approach depending on whether you are using an elastic IP for your server or whether it is behind a load balancer,