I finally tried the global snapshots stuff below is what I did.

I have taken data from all individual nodes from a single DC after changing the numerical part(this numerical part can have only a max value of 2147483647).

1.My individual nodes were having 12Gb odd data so after combining it was around 77 Gb of data.

2.My new ring had exact configuration in terms of number of nodes,RF and token distribution.

3.I copied all the data on all individual nodes and ran cleanup.

4.After running cleanup all the nodes had an data in range of 34Gb-38Gb .

5.The data on all the nodes was correct validated against the original ring.

6.One of the node in a DC had data close to 68Gb and running cleanup didnt triggered anything

What I can't understood by now is the 

1.Is the data size correct . I have RF=3 and 6 nodes in one DC as on the other . Is it because ((77 * 3)/6
2.Why was one node having 68Gb data .

Below is the ring status

Address         DC          Rack        Status State   Load            Owns    Token
                                                                               155962751505430122790891384580033478656
11.60     DC1         RC1         Up     Normal  38.83 GB        8.33%   0
6.136   DC2         RC1         Up     Normal  34.49 GB        8.33%   14178431955039101857246194831382806528
11.61     DC1         RC2         Up     Normal  37.62 GB        8.33%   28356863910078203714492389662765613056
6.137   DC2         RC2         Up     Normal  33.96 GB        8.33%   42535295865117307932921825928971026432
11.62     DC1         RC1         Up     Normal  36.91 GB        8.33%   56713727820156407428984779325531226112
6.138   DC2         RC1         Up     Normal  34.12 GB        8.33%   70892159775195516369780698461381853184
11.63     DC1         RC2         Up     Normal  37.63 GB        8.33%   85070591730234615865843651857942052864
6.139   DC2         RC2         Up     Normal  33.84 GB        8.33%   99249023685273724806639570993792679936
11.64     DC1         RC1         Up     Normal  38.83 GB        8.33%   113427455640312814857969558651062452224
6.140   DC2         RC1         Up     Normal  34.37 GB        8.33%   127605887595351923798765477786913079296
11.65     DC1         RC2         Up     Normal  39.54 GB        8.33%   141784319550391032739561396922763706368
6.141   DC2         RC2         Up     Normal  68.29 GB        8.33%   155962751505430122790891384580033478656

Regards,
Shubham

From: Tamar Fraenkel [tamar@tok-media.com]
Sent: Wednesday, May 02, 2012 11:13 AM
To: user@cassandra.apache.org
Subject: Re: Taking a Cluster Wide Snapshot

I think it make's sense and would be happy if you can share the incremental snapshot scripts.
Thanks!
Tamar Fraenkel 
Senior Software Engineer, TOK Media 






On Tue, May 1, 2012 at 11:06 AM, Shubham Srivastava <Shubham.Srivastava@makemytrip.com> wrote:
On another thought I am writing a code/script for taking a backup of all the nodes in a single DC , renaming data files with some uid and then merging them . The storage however would happen on some storage medium nas for ex which would be in the same DC. This would help in data copying a non hefty job.

Hopefully the one single DC data(from all the nodes in this DC) should give me the complete data just in case if RF >=1 .

The next improvement would be do do the same on incremental snapshots so that once you have a baseline data all the rest would be collecting chunks of increments alone and merging it with the original global snapshot.

I have do the same on each individual DC's.

Do you guys agree?

Regards,
Shubham


From: Tamar Fraenkel [tamar@tok-media.com]
Sent: Tuesday, May 01, 2012 10:50 AM

To: user@cassandra.apache.org
Subject: Re: Taking a Cluster Wide Snapshot

Thanks for posting the script.
I see that the snapshot is always a full one, and if I understand correctly, it replaces the old snapshot on S3. Am I right?

Tamar Fraenkel 
Senior Software Engineer, TOK Media 






On Thu, Apr 26, 2012 at 9:39 AM, Deno Vichas <deno@syncopated.net> wrote:
On 4/25/2012 11:34 PM, Shubham Srivastava wrote:
Whats the best way(or the only way) to take a cluster wide backup of Cassandra. Cant find much of the documentation on the same.

I am using a MultiDC setup with cassandra 0.8.6.


Regards,
Shubham
 here's how i'm doing in AWS land using the DataStax AMI via a nightly cron job.  you'll need pssh and s3cmd -


#!/bin/bash
cd /home/ec2-user/ops

echo "making snapshots"
pssh -h prod-cassandra-nodes.txt -l ubuntu -P 'nodetool -h localhost -p 7199 clearsnapshot stocktouch'
pssh -h prod-cassandra-nodes.txt -l ubuntu -P 'nodetool -h localhost -p 7199 snapshot stocktouch'

echo "making tar balls"
pssh -h prod-cassandra-nodes.txt -l ubuntu -P -t 0 'rm `hostname`-cassandra-snapshot.tar.gz'
pssh -h prod-cassandra-nodes.txt -l ubuntu -P -t 0 'tar -zcvf `hostname`-cassandra-snapshot.tar.gz /raid0/cassandra/data/stocktouch/snapshots'

echo "coping tar balls"
pslurp -h prod-cassandra-nodes.txt -l ubuntu /home/ubuntu/*cassandra-snapshot.tar.gz .

echo "tar'ing tar balls"
tar -cvf cassandra-snapshots-all-nodes.tar 10*

echo "pushing to S3"
../s3cmd-1.1.0-beta3/s3cmd put cassandra-snapshots-all-nodes.tar  s3://stocktouch-backups

echo "DONE!"