Yes, a power outage would be one cause, but any hardware failure of the active cluster node that causes the other to assume the active role will suffice. Best practice is to literally force a power outage on the failed node when this happens via a STONITH device (acronym for "shoot the other node in the head"). Each of our servers has its power routed through one of these devices with a serial port connected to the other server. Without STONITH devices, you run the risk of a "split brain" situation if the two servers lose contact with each other for any reason. The backup node assumes the active role when it doesn't receive regular heartbeats from the active node, but if this is simply due to a network issue between the nodes, the original active node may still be serving clients. Now you have two active nodes serving different clients from their own individual copies of the data. I've experienced that situation once, and I hope to never go through it again.
-John -----Original Message----- From: u2-users-boun...@listserver.u2ug.org [mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of Wjhonson Sent: Tuesday, September 03, 2013 4:32 PM To: u2-users@listserver.u2ug.org Subject: Re: [U2] REPLICATING DATA Under what scenario would the overflow record not get written? You mean a power outage? Or what exactly? -----Original Message----- From: John Hester <jhes...@momtex.com> To: U2 Users List <u2-users@listserver.u2ug.org> Sent: Tue, Sep 3, 2013 3:49 pm Subject: Re: [U2] REPLICATING DATA Daniel's post reminded me that I should probably qualify my original post by adding that you have to take special precautions when using 3rd party replication software with U2. Specifically, it's not safe to have overflow in hashed files because the overflow pointer and overflow data require two separate writes to disk. If a failover occurs when only one of the two writes has been completed, you'll likely end up with a corrupted file. I've eliminated this issue in our environment by keeping all hashed files sized to have no overflow and only using dynamic files for temporary report data. This probably isn't feasible in a lot of environments. -John -----Original Message----- From: u2-users-boun...@listserver.u2ug.org [mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of John Hester Sent: Tuesday, September 03, 2013 11:40 AM To: U2 Users List Subject: Re: [U2] REPLICATING DATA We've been using LifeKeeper from SIOS to replicate UV for around 10 years. I think it's now been rebranded as "Protection Suite": http://us.sios.com/linux-high-availability-replication-enterprise/ It can run on Linux or Windows. We're running UV 10.2.7 on RH EL 5.1. -John _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users
