With RF=2 & CL=ONE, take care on that you still have chance to read old data which is not replicated yet.
Maki From iPhone On 2011/03/26, at 5:10, Jared Laprise <ja...@webonyx.com> wrote: > No, what initially started it all was that I needed to increase my EC2 server > instance size. So I removed said server from the load balancer, stopped > Cassandra, and then shutdown the server in order to change the instance type. > I assumed the other node had all the data and everything should keep running > without issue. Almost immediately I realized I was missing a bunch of data. > Not fully understanding what happened I was hesitant to bring up the other > node again for fear of data loss (again because I didn't understand what had > happened). I ended up bringing the other node back online and then everything > seemed to snap back it expected working order. > > Although after all the help from the Cassandra community I have a much better > understanding of why and how my situation happened, there was still one > strange side effect I noticed. For context, I store user accounts and other > account information in Cassandra. When the second node was offline and I > tried to log into the site, I got an error saying invalid password. Out of > curiosity I logged into the cassandra-cli tool and looked at what columns and > values were present for my user account. My User CF seemed to have data > stored from right before I added the second node. I found that really strange > assuming that Cassandra doesn't keep any historical or versioned data? Again, > once the second node was back online both servers showed the expected more > current data. > > Today I'm preparing to increase my replication factor to 2 and have been > reading about the proper way to do that. Although I've found bits and pieces, > I haven't found any definitive explanation on how to do it. Could someone > please sanity check my intended approach? > > 1. Change the RF to 2 and restart Cassandra on both nodes > 2. Run `nodetool repair` on both nodes, one at a time as to not halt up both > servers (will that sync data between the nodes?) > > In a 2 node environment and RF=2 using consistency level of ONE would still > ensure data is replicated to both servers, correct? > > -----Original Message----- > From: Sylvain Lebresne [mailto:sylv...@datastax.com] > Sent: Friday, March 25, 2011 3:01 AM > To: user@cassandra.apache.org > Cc: Jared Laprise > Subject: Re: URGENT HELP PLEASE! > > On Fri, Mar 25, 2011 at 1:49 AM, Jared Laprise <ja...@webonyx.com> wrote: >> Hello all, I'm running 2 Cassandra 6.5 nodes and I brought down the >> secondary node and restarted the primary node. After Cassandra came >> back up all data has been reverted to several months ago. > > Out of curiosity, when you said 'brought down the secondary node', did that > involved a decomission or removeToken ? If so, I have an explanation for you. > > -- > Sylvain > > >> I could really use some incite here, this is a production website and >> I need to act quickly. I have a cron job that takes a snapshot every >> night, but even with that I tried to restore a snapshot on my local >> development environment and it was also missing a ton of data. >> >> >> >> Any help will be so appreciated. >> >> >> >>
