Today I need to bring that data center back in. It is not 2-3 days out dated. I have two options:

1) Treat this as a new data center and let the nodes sync from scratch, or
2) Bring the nodes back up with all the data in place and do a repair.
As long as the nodes were down for less than gc_grace_seconds i would bring the old ones back with their data and run repair. 

If possible avoid having the application read from them until its complete. 

There are 4 nodes in both data centers, with RF=2.
Id recommend moving to RF 3 if you use QUORUM. 

Cheers

-----------------
Aaron Morton
New Zealand
@aaronmorton

Co-Founder & Principal Consultant
Apache Cassandra Consulting
http://www.thelastpickle.com

On 26/10/2013, at 2:33 am, Oleg Dulin <oleg.dulin@gmail.com> wrote:

I am using Cassandra 1.1.11 and plan on upgrading soon, but in the meantime here is what happened.

I couldn't run repairs because of a slow WAN pipe, so i removed the second data center from the cluster.

Today I need to bring that data center back in. It is not 2-3 days out dated. I have two options:

1) Treat this as a new data center and let the nodes sync from scratch, or
2) Bring the nodes back up with all the data in place and do a repair.

We are talking about 30-40Gigs per node. There are 4 nodes in both data centers, with RF=2.


--
Regards,
Oleg Dulin
http://www.olegdulin.com