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From Damien Katz <dam...@apache.org>
Subject Re: Backup of couchdb
Date Fri, 22 Aug 2008 14:17:52 GMT

On Aug 22, 2008, at 3:47 AM, Jan Lehnardt wrote:

>
> On Aug 22, 2008, at 08:12, Niket Patel wrote:
>
>>
>> On Aug 22, 2008, at 11:09 AM, Jason Huggins wrote:
>>
>>> Just to be clear... is it okay to make a "hot backup" of that file
>>> while the server is still running? (I would think so, give it's
>>> append-only storage design.)
>>
>> More information on this will be helpful from couchdb developer.
>> If backup doesn't have some recently added records between backup  
>> start and finish..
>> thats fine
>>
>> But if this can corrupt db file, we have to think other backup  
>> options
>> replication should not considered as backup.
>
>
> After each write, a database file is guaranteed to be consistent on
> disk (unless you are on an OS that doesn't handle fsync() properly).
>
> If you disable writes to a database during the time of a backup, you
> can make a "hot" copy. You might not consider that "hot" anymore
> though. Reads can still go to the file.

Actually, you can copy a live database file from the OS at anytime  
without problem. Doesn't matter if its being updated, or even if its  
being compacted, the CouchDB never-overwrite storage format ensures it  
should just work without issue.

-Damien


>
>
> Or have two nodes, one of which is your live-node and the other one
> is your backup-node. Have the backup-node replicate from the live
> node up to a certain point. Then shut it down (or leave it idle) and
> make a filesystem copy of the replicated database.
>
> Use filesystem snapshots. In theory you should be able to grab
> a complete and live snapshot from under CouchDB's feet, I have
> never done this though and you should verify that it works :)
>
> Cheers
> Jan
> --


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