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From Ian Boston <...@tfd.co.uk>
Subject Re: Hot-backup strategy
Date Tue, 25 May 2010 11:35:14 GMT

On 25 May 2010, at 12:22, Vidar Ramdal wrote:

>> On 25 May 2010, at 11:56, Vidar Ramdal wrote:
>>> According to [1]: "Database persistence managers: many databases
>>> support online backup, so if you use that you should be safe.".
>>> Does this mean that a hot backup is "guaranteed" to be consistent when:
>>> - The datastore is backed up
>>> - The database is backed up using the database vendor's tools
>>> [1] http://wiki.apache.org/jackrabbit/BackupAndMigration
> On Tue, May 25, 2010 at 1:12 PM, Ian Boston <ieb@tfd.co.uk> wrote:
>> From a RDBMS point of view, if the vendors tools claim consistency, then that what
you will get, only for the RDBMS.
>> You will need to do
>> DB backup
>> Datastore (assuming file persistence) backup , since its append only and will be
consistent with the DB.
>> in that order.
> Thanks for your quick reply.
> OK, so backup the DB first, then the datastore directory. Fine.
> Just to be clear: You're saying that a hot RDBMS backup should be
> consistent (thus restorable), even when the backup is run while
> Jackrabbit is writing to the DB?
> Do you yourself use this procedure?

Yes, on MySQL we use mysqldump against a mysql slave connected to a master DB. 
Mysql unfortunately does some locking of tables that makes things runs slow, so thats why
we do it on a slave. (thats how it guarantees consistency)

For Oracle, there is a well documented procedure for hot archive logging and hot backups.
For others there are equivalents.

The only thing you might consider is although you will get a consistent DB and the DB will
have all the state it expects in the Datastore (although the Datastore may have more state
than the DB expects), if your users are half way though a non transacted operation (ie web
form flow) you might get their state half way through.  Not much you can do about that, except
at the application level.


>> You might also need so capture the local lucene index state, but that starts to get
complicated. I cant remember how it rebuilds from scratch (if it does)?
> The Lucene index is rebuilt if it is missing on Jackrabbit startup, AFAIK.
> -- 
> Vidar S. Ramdal <vidar@idium.no> - http://www.idium.no
> Sommerrogata 13-15, N-0255 Oslo, Norway
> + 47 22 00 84 00 / +47 22 00 84 76
> Quando omni flunkus moritatus!

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