RE: Falconstor/IPStor with Clariion, EMC Timefinder with Symmetrix
- From: Michael Boligan <michael.boligan.b@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 24 Mar 2004 09:43:00 -0500
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.
.... Actually 3 times, if you count the rollback segment. I think you are
right, Hot backup is a much better option, and less expensive.
Mike
|---------+----------------------------->
| | "Lex de Haan" |
| | <lex.de.haan@natur|
| | aljoin.nl> |
| | Sent by: |
| | oracle-l-bounce@fr|
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| | 03/24/2004 08:26 |
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| | Please respond to |
| | oracle-l |
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| To: <oracle-l@xxxxxxxxxxxxx>
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| cc:
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| Subject: RE: Falconstor/IPStor with Clariion, EMC Timefinder with
Symmetrix |
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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@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Michael Boligan
Sent: woensdag 24 maart 2004 13:52
To: oracle-l@xxxxxxxxxxxxx
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@natur|
| | aljoin.nl> |
| | Sent by: |
| | oracle-l-bounce@fr|
| | eelists.org |
| | |
| | |
| | 03/24/2004 06:27 |
| | AM |
| | Please respond to |
| | oracle-l |
| | |
|---------+----------------------------->
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| To: <oracle-l@xxxxxxxxxxxxx>
|
| cc:
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| Subject: RE: Falconstor/IPStor with Clariion, EMC Timefinder with
Symmetrix |
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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@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Carel-Jan Engel
Sent: woensdag 24 maart 2004 10:12
To: oracle-l@xxxxxxxxxxxxx
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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