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From Marcos Ortiz <>
Subject Re: Migration question
Date Wed, 15 Jun 2011 03:50:22 GMT

El 6/14/2011 1:43 PM, Eric Czech escribió:
> Thanks Aaron.  I'll make sure to copy the system tables.
> Another thing -- do you have any suggestions on raid configurations 
> for main data drives?  We're looking at RAID5 and 10 and I can't seem 
> to find a convincing argument one way or the other.
Well, I learned from administrating other databases (like PostgreSQL and 
Oracle) that RAID 10 is the best solution for data. With RAID 5, the 
discs suffer a lot for the excesive I/O and It can arrive to
data lost. You can search about the "RAID 5 Write Hole" to view this.

> Thanks again for your help.
> On Mon, Jun 6, 2011 at 5:45 AM, aaron morton < 
> <>> wrote:
>     Sounds like you are OK to turn off the existing cluster first.
>     Assuming so, deliver any hints using JMX then do a nodetool flush
>     to write out all the memtables and checkpoint the commit logs. You
>     can then copy the data directories.
>     The System data directory contains the nodes token and the schema,
>     you will want to copy this directory. You may also want to copy
>     the cassandra.yaml or create new ones with the correct initial tokens.
>     The nodes will sort themselves out when they start up and get new
>     IP's, the important thing to them is the token.
>     Cheers
>     -----------------
>     Aaron Morton
>     Freelance Cassandra Developer
>     @aaronmorton
>     On 6 Jun 2011, at 23:25, Eric Czech wrote:
>     > Hi, I have a quick question about migrating a cluster.
>     >
>     > We have a cassandra cluster with 10 nodes that we'd like to move
>     to a new DC and what I was hoping to do is just copy the SSTables
>     for each node to a corresponding node in the new DC (the new
>     cluster will also have 10 nodes).  Is there any reason that a
>     straight file copy like this wouldn't work?  Do any system tables
>     need to be moved as well or is there anything else that needs to
>     be done?
>     >
>     > Thanks!

Marcos Luís Ortíz Valmaseda
  Software Engineer (UCI)

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