Despite storing a replica in the "backup node", what is the guarantee that the "backup node" has all the data? Unless you make consistency a priority over availability of your cluster. I could think of another approach. You can design your cluster with a topology such that your work load is split into to virtual datacenters and you keep replicas in both datacenters. During read you can do LOCAL_QUORUM and during write you can do EACH_QUORUM. With this set up you can call the second virtual datacenter as a backup. Sorry there are no tapes involved here. Thanks,KumarFrom: maria.cama...@nsn.com To: user@cassandra.apache.org Subject: RE: Backup Cassandra to Date: Fri, 13 Jun 2014 10:04:49 +0000
Thanks a lot for your responses. Maria. From: ext Jabbar Azam [mailto:aja...@gmail.com] Sent: Thursday, June 12, 2014 10:09 PM To: user@cassandra.apache.org Cc: Jack Krupansky Subject: Re: Backup Cassandra to Yes, I never thought of that. Thanks Jabbar Azam On 12 June 2014 19:45, Jeremy Jongsma <jer...@barchart.com> wrote: That will not necessarily scale, and I wouldn't recommend it - your "backup node" will need as much disk space as an entire replica of the cluster data. For a cluster with a couple of nodes that may be OK, for dozens of nodes, probably not. You also lose the ability to restore individual nodes - the only way to replace a dead node is with a full repair. On Thu, Jun 12, 2014 at 1:38 PM, Jabbar Azam <aja...@gmail.com> wrote: There is another way. You create a cassandra node in it's own datacentre, then any changes going to the main cluster will be replicated to this node. You can backup from this node. In the event of a disaster the data from both clusters and wiped and then replayed to the individual node. The data will then be replicated to the main cluster. This will also work for the case when the main cluster increases or decreases in size. Thanks Jabbar Azam On 12 June 2014 18:27, Andrew <redmu...@gmail.com> wrote: There isn’t a lot of “actual documentation” on the act of backing up, but I did research for my own company into the act of backing up and unfortunately, you’re not going to have a similar setup as Oracle. There are reasons for this, however. If you have more than one replica of the data, that means each node in the cluster will likely be holding it’s own unique set of data. So you would need to back up the ENTIRE set of nodes in order to get an accurate snapshot. Likewise, you would need to restore it to the cluster of the same size in order to restore it (and then run refresh to tell Cassandra to reload the tables from disk). Copying the snapshots is easy—it’s just a bunch of files in your data directory. It’s even smaller if you use incremental snapshots. I’ll admit, I’m no expert on tape drives, but I’d imagine it’s as easy as copy/pasting the snapshots to the drive (or whatever the equivalent tape drive operation is). What you (and I, admittedly) would really like to see is a way to back up all the logical *data*, and then simply replay it. This is possible on Oracle because it’s typically restricted to either one (plus maybe one or two standbys) that don’t “share” any data. What you could do, in theory, is literally select all the data in the entire cluster and simply dump it to a file—but this could take hours, days, or even weeks to complete, depending on the size of your data, and then simply re-load it. This is probably not a great solution, but hey—maybe it will work for you. Netflix (thankfully) has posted a lot of their operational observations and what not, including their utility Priam. In their documentation, they include some overviews of what they use: https://github.com/Netflix/Priam/wiki/Backups Hope this helps! Andrew On June 12, 2014 at 6:18:57 AM, Jack Krupansky (j...@basetechnology.com) wrote: The doc for backing up – and restoring – Cassandra is here: http://www.datastax.com/documentation/cassandra/2.0/cassandra/operations/ops_backup_restore_c.html That doesn’t tell you how to move the “snapshot” to or from tape, but a snapshot is the starting point for backing up Cassandra. -- Jack Krupansky From: Camacho, Maria (NSN - FI/Espoo) Sent: Thursday, June 12, 2014 4:57 AM To: user@cassandra.apache.org Subject: Backup Cassandra to Hi there, I'm trying to find information/instructions about backing up and restoring a Cassandra DB to and from a tape unit. I was hopping someone in this forum could help me with this since I could not find anything useful in Google :( Thanks in advance, Maria
