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RE: Falconstor/IPStor with Clariion, EMC Timefinder with Symmetrix

From: Lex de Haan <lex.de.haan_at_naturaljoin.nl>
Date: Wed, 24 Mar 2004 17:34:18 +0100
Message-ID: <JFEEIGBIDOCCDALDIPLNGEHACBAA.lex.de.haan@naturaljoin.nl>


could be -- I am pretty ignorant in this area. I was only interpreting the explanation from the email thread; if my conclusion is wrong, the premise must have been wrong too ;-)

and although this is not my area of expertise, I still guess that leaving the data files untouched, writing all modified blocks to different places on disk,
while maintaining pointers to all changed blocks still is way less efficient as leaving it up to the Oracle server itself to avoid fractioned blocks.

additions/corrections welcome,
Lex.

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Yechiel Adar Sent: woensdag 24 maart 2004 17:33
To: oracle-l_at_freelists.org
Subject: Re: Falconstor/IPStor with Clariion, EMC Timefinder with Symmetrix

Hello Lex

I think that you got it wrong. The storage system does not write the block twice.
Instead it will write the new block to another place on the disk and will update the pointers only. The old block stays in place and can not be overwritten as it is marked as used by the snapshot.

Yechiel Adar
Mehish
----- Original Message -----
From: "Lex de Haan" <lex.de.haan_at_naturaljoin.nl> To: <oracle-l_at_freelists.org>
Sent: Wednesday, March 24, 2004 3:26 PM
Subject: RE: Falconstor/IPStor with Clariion, EMC Timefinder with Symmetrix

> Mike, Carel-Jan,
>
> this sounds like a pretty expensive solution (and I am not talking money
> here) -- just imagine how many I/O activity you typically have against an
> online Oracle database... this means that after the "snapshot point in
time"
> you basically start writing every block twice -- once to the database, and
> once to the snapshot.
>
> well, I can tell you, the Oracle mechanism (activated by putting files in
> backup mode) is definitely cheaper, because it is a more intelligent
> algorithm; it only writes full block images to the redo log when needed
for
> recoverability, and definitely NOT for every change ...
>
> cheers,
> Lex.
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Michael Boligan
> Sent: woensdag 24 maart 2004 13:52
> To: oracle-l_at_freelists.org
> Subject: RE: Falconstor/IPStor with Clariion, EMC Timefinder with
> Symmetrix
>
>
>
>
>
>
> Carel-Jan,
>
> We are looking at using Compaq's Virtual Snapshot Replicator for one
> of
> our Sqealserver databases. The way it works is that when you create a
> snapshot
> it creates a file which contains a pointer to the database file. When
> someone
> changes the database, the before image is written to the snapshot file.
At
> this
> point the file is no longer just a pointer it containts before image data.
> The
> backup, will backup the snapshot, not the database file. This provides a
> consistent image. This is very different than EMC Timefinder, which is
used
> to
> backup a mirrored database. When you break the mirror Timefinder ensures
> that
> no data is in the buffers that would make the mirrored data incomplete.
At
> this
> point you can bring the mirrored database down and get a cold backup, then
> resync the mirrors. I have not used it so I can't give any feedback as to
> if it
> works as advertised or not.
> Timefinder is a better option, in my opinion, and more expensive.
> Snapshot replication is for the lower end disk arrays that can't provide
> anything like Timefinder because the array doesn't have an on board CPU.
>
> HTH,
> Mike
>
>
> |---------+----------------------------->
> | | "Lex de Haan" |
> | | <lex.de.haan_at_natur|
> | | aljoin.nl> |
> | | Sent by: |
> | | oracle-l-bounce_at_fr|
> | | eelists.org |
> | | |
> | | |
> | | 03/24/2004 06:27 |
> | | AM |
> | | Please respond to |
> | | oracle-l |
> | | |
> |---------+----------------------------->
>
>
>---------------------------------------------------------------------------
> --------------------------------------------|
> |
> |
> | To: <oracle-l_at_freelists.org>
> |
> | cc:
> |
> | Subject: RE: Falconstor/IPStor with Clariion, EMC Timefinder
with
> Symmetrix |
>
>
>---------------------------------------------------------------------------
> --------------------------------------------|
>
>
>
>
> Carel-Jan,
>
> the *one and only* reason why you need to put Oracle data files in backup
> mode is to avoid fractured blocks -- that is, ending up with Oracle blocks
> (spanning multiple OS blocks) with the header and footer out of sync.
> I don't know the technology of "snapshotting" all data files in a single
> atomic action -- sounds interesting to me... how do they do this? be
> careful, this might be marketing language, with some vipers under the
grass
> ;-)
>
> anyway, if it is really true that they can guarantee this "atomic
> snapshotting" you would be able to do hot backups without the need to put
> your tablespaces or data files in backup mode. By the way, you don't
really
> need it at the database level; at the data file level it is good enough.
>
> Whether this is supported, that's another story.
>
> Cheers,
> Lex.
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Carel-Jan Engel
> Sent: woensdag 24 maart 2004 10:12
> To: oracle-l_at_freelists.org
> Subject: Falconstor/IPStor with Clariion, EMC Timefinder with Symmetrix
>
>
> Hi list,
>
> Does anyone know these products for HA-solutions? Especially, is it
> possible/certified to snapshot databases without putting the database in
> backup mode?
>
> The idea behind it is that all datafiles (incl. control and online
> redolog) are snapshotted in one single atomic action. The snapshot is
> stored at a local mirror, and asynchronously transferred to the DR-site.
> Failover can be performed by starting and (auto)recovering the database at
> the DR site. Because all files were copied in the state they were in one
> point in time, starting the database at the remote site should be the same
> as starting a database after a power failure.
>
> I'm not interested in all kinds of other HA solutions, the site I'm
> currently working for has implemented these solutions, but needs
> verification. It's hard to get commitment from the vendors that their
> products are certified for Oracle, although they advised and sold the
> solution :-(.
>
>
> Thanks, Carel-Jan
>
> ===
> If you think education is expensive, try ignorance. (Derek Bok)
> ===
>
>
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Received on Wed Mar 24 2004 - 10:37:50 CST

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