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From aaron morton <aa...@thelastpickle.com>
Subject Re: Question on Cassandra Snapshot
Date Sun, 17 Feb 2013 17:37:34 GMT
> With incremental_backup turned OFF in Cassandra.yaml - Are all SSTables are under /data/TestKeySpace/ColumnFamily
at all times?
No. 
They are deleted when they are compacted and no internal operations are referencing them.


> With incremental_backup turned ON in cassandra.yaml - Are current SSTables under /data/TestKeySpace/ColumnFamily/
with a hardlink to /data/TestKeySpace/ColumnFamily/backups? 
Yes, sort of. 
*All* SSTables ever created are in the backups directory. 
Not just the ones currently "live".

> Lets say I have taken snapshot and moved the /data/TestKeySpace/ColumnFamily/snapshots/<snapshot-name>/*.db
to tape, at what point should I be backing up *.db files from /data/TestKeySpace/ColumnFamily/backups
directory. Also, should I be deleting the *.db files whose inode matches with the files in
the snapshot? Is that a correct approach? 
Backup all files in the snapshots. There may be non .db extensions files if you use levelled
compactions
When you are finished with the snapshot delete it. If the inode is not longer referenced from
the live data dir it will be deleted. 

> I noticed /data/TestKeySpace/ColumnFamily/snapshots/<timestamp>-ColumnFamily/ what
are these <timestamp> directories?
Probably automatic snapshot from dropping KS or CF's

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 16/02/2013, at 4:41 AM, S C <asf11@outlook.com> wrote:

> I appreciate any advise or pointers on this.
> 
> Thanks in advance.
> 
> From: asf11@outlook.com
> To: user@cassandra.apache.org
> Subject: Question on Cassandra Snapshot
> Date: Thu, 14 Feb 2013 20:47:14 -0600
> 
> I have been looking at incremental backups and snapshots. I have done some experimentation
but could not come to a conclusion. Can somebody please help me understanding it right?
> 
> /data is my data partition
> 
> With incremental_backup turned OFF in Cassandra.yaml - Are all SSTables are under /data/TestKeySpace/ColumnFamily
at all times?
> With incremental_backup turned ON in cassandra.yaml - Are current SSTables under /data/TestKeySpace/ColumnFamily/
with a hardlink to /data/TestKeySpace/ColumnFamily/backups? 
> Lets say I have taken snapshot and moved the /data/TestKeySpace/ColumnFamily/snapshots/<snapshot-name>/*.db
to tape, at what point should I be backing up *.db files from /data/TestKeySpace/ColumnFamily/backups
directory. Also, should I be deleting the *.db files whose inode matches with the files in
the snapshot? Is that a correct approach? 
> I noticed /data/TestKeySpace/ColumnFamily/snapshots/<timestamp>-ColumnFamily/ what
are these <timestamp> directories?
> 
> Thanks in advance. 
> SC


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