----- Original Message -----
After some lengthy discussion with Stefan, I think the migration tool needs to be run while the server is offline or possibly in maintenance mode. The best time to run the tool would be prior to running the RHQ installer. A problem with doing the data migration while the server is running is that we could wind up with skews in the aggregate data. The easiest and fastest way to ensure data is consistent for both pre- and post-upgrade is to run the data migration while the server is down.
Whether this approach is feasible or not could very well depend on the speed of the migration -How long does our normal upgrade take today? I'm not aware of folks saying that was too long -If it takes hours/days to move data during upgrade then that may simple not be an option. Could a portion of the data be moved while the server is live?
- John
On Jan 2, 2013, at 6:20 PM, Stefan Negrea snegrea@redhat.com wrote:
Hello Everybody,
With new Cassandra based metrics storage system, existing data will need to be migrated out of existing SQL storage to Cassandra. I put together a simple design document for the data migration tool that will be delivered with RHQ when the new metrics storage system is completed.
My initial thoughts about the tool are:
- Restartable migration process, this will be especially useful
for users with large amounts of metrics. 2) Favour robustness over performance because this migration will be done only once. 3) Make the tool external to the product (not part of the installation), so user can do the migration ahead of the upgrade.
Here is the full design document: https://docs.jboss.org/author/display/RHQ/Metrics+Data+Migration+-+Design
Feedback is more than welcomed since this tool is still in the early planning stages.
Thank you, Stefan Negrea
Software Engineer
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