Re: Dataguard / Archive Logs
- From: Carel-Jan Engel <cjpengel.dbalert@xxxxxxxxx>
- To: adar76@xxxxxxxxxxxx
- Date: Thu, 02 Jun 2005 12:29:09 +0200
Yechiel,
I can't see the different purposes. Both are meant for keeping a DR site
up-to-date. Logical Standby or SQL-Apply is added later to Data Guard,
and I do not see this option as a solution for HA. It can be useful for
replicating data to another database, but HA is quite another chapter.
Physical Standby is basically meant for HA, with some extra features.
Storage replication is justified for data that can't be replicated
otherwise (i.e. data outside of the databases). Data Guard is more
feature rich than storage replication, but has the same purpose:
offering HA.
I prefer combining them: Data Guard for the database, storage
replication for the rest. If you use Oracle Files, you don't need the
latter. As Tom Kyte says: "everything in the database" ;-)
Best regards,
Carel-Jan Engel
===
If you think education is expensive, try ignorance. (Derek Bok)
===
On Thu, 2005-06-02 at 12:46, Yechiel Adar wrote:
> I think that SAN replication and Data Guard have two different purposes:
>
> SAN replication is for replication of the entire site to disaster
> recovery site.
>
> Data Guard is for moving the data in the database to another database to
> guard against database loss, due to human error or server failure, or to
> send that specific data to a remote site.
>
> Yechiel Adar, Mehish
>
> David Sharples wrote:
>
> >wow, you should write a book on this stuff :-)
> >
> >the san would be synchronous writes.
> >
> >So If i can try to put it simply - it would work that way, but
> >dataguards on the face of it seems the better, cheaper solution ?
> >
> >On 6/1/05, Carel-Jan Engel <cjpengel.dbalert@xxxxxxxxx> wrote:
> >
> >
> >>David,
> >>=20
> >>Is the SAN replicating synchronously or asynchronously?
> >>Data Guard needs less bandwidth than storage based replication. Most of t=
> >>
> >>
> >he
> >
> >
> >>times SAN's are configured to replicate asynchrously. Just think of the
> >>amount of data that needs to be sent over when storage is replicated: Red=
> >>
> >>
> >o
> >
> >
> >>writes (all members), archive copies (maybe also redundant?), the writes =
> >>
> >>
> >to
> >
> >
> >>data files, and the updates of the controlfile. Mind that storage based
> >>replication is often disk block based, or even disktrack-based! You can
> >>imagine what amount of data needs to go through the pipe for that. Compar=
> >>
> >>
> >e
> >
> >
> >>that with just sending the redo entries with Data Guard. The standby site
> >>will take care of applying them, writing to data files and performing the
> >>archive job locally.=20
> >>
> >>
> >>
> >--
> >//www.freelists.org/webpage/oracle-l
> >
> >
> >
> --
> //www.freelists.org/webpage/oracle-l
--
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