backup strategy using HDS - shadow image, true copy
Poster was testing HDS ShadowImage/TrueCopy disk snapshots as an external backup for IDS 7.31/9.31, using 'onmode -c block/unblock' around the split and 'onbar -r -e' to restore, but occasionally ended up with corruption (lost logdbs mirror, a chunk offline when applying logs). One reply wrongly claimed such tools can't work; others confirmed the approach (IBM calls it External Backup and Restore) is valid if block/unblock is used. IBM's Martin Fuerderer gave the fix/rules: back up all chunks, including mirrors, within one block/unblock bracket with all dbspaces/chunks online; no partial backups or partial cold+warm restores; restore everything; verify with oncheck or a test restore, since ON-Bar can't validate an external backup. Also noted problems from a down BLOBspace chunk during log backup.
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Hi, We are presently testing shadow imange and true copy, as a backup solution for our Informix database. This will replace the Informix Onbar backups. While performing some recovery testing using this new method, I got corrupted database. Anybody using shadow image or true copy as database backup solution? Any comments will be much appreciated. Regards
we are using the onmode -c block/unblock commands to synchronize the
db and
using the onbar -r -e (external backup tools) to recover it.
we did many recovery test, with log and without logs, most of the time
successfully except for these 4 times that I got the corruption.
External backup tools are not supported by Informix, but onmode and onbar
cmds exist for this type of backup......
-----Original Message-----
From: Robert Roussey
[mailto:IMCEAEX-_O=SPIRITAIR_OU=RESCT_CN=RECIPIENTS_CN=ROBERTRO@SpiritAir.co
m]
Sent: Friday, November 26, 2004 1:55 PM
To: Lavoie, Diane; ids@iiug.org
Subject: RE: backup strategy using HDS - shadow image, true copy [3789]
Neither of those will work because they totally ignore the Informix
timestamp (used for all backups and restores) that exists on every data page
and in the system catalog. The only way those utilities would work is if
you shut down informix and did them.
Bob Roussey
Spirit Airlines
Informix/Unix Administration
Phone: 586.741.8991
e-mail: RobertRo@SpiritAir.com
-----Original Message-----
From: forum.subscriber@iiug.org [ mailto:forum.subscriber@iiug.org
<mailto:forum.subscriber@iiug.org> ] On Behalf Of Lavoie, Diane
Sent: Friday, November 26, 2004 11:28 AM
To: ids@iiug.org
Subject: backup strategy using HDS - shadow image, true copy [3789]
Hi,
We are presently testing shadow imange and true copy, as a backup solution
for our Informix database.
This will replace the Informix Onbar backups. While performing some recovery
testing using this new
method, I got corrupted database.
Anybody using shadow image or true copy as database backup solution? Any
comments will be much appreciated.
Regards
Did you block the database with
onmode -c blockwhile splitting the disks (taking the snapshot) ?
That is essential to get a consistent snapshot!
You should be able to start the database from that
image (without applying logical logs).
But if you want to recover until the most recent
point in time you will need Onbar for the logical
logs.
Regards,
Andreas Kutsche
> -----Ursprüngliche Nachricht-----
> Von: forum.subscriber@iiug.org [mailto:forum.subscriber@iiug.org]Im
> Auftrag von Lavoie, Diane
> Gesendet: Freitag, 26. November 2004 17:28
> An: ids@iiug.org
> Betreff: backup strategy using HDS - shadow image, true copy [3789]
>
>
> Hi,
>
> We are presently testing shadow imange and true copy, as a
> backup solution
> for our Informix database.
>
> This will replace the Informix Onbar backups. While
> performing some recovery
> testing using this new
> method, I got corrupted database.
>
> Anybody using shadow image or true copy as database backup
> solution? Any
> comments will be much appreciated.
>
> Regards
>
>
>
Hi,
the description of what you're doing sounds about right.
(BTW: we call it "External Backup and Restore".)
What version of IDS are you using ?
Can you describe the corruptions and the circumstances
where they occurred in more detail ?
Regards,
Martin
--
Martin Fuerderer
IBM Informix Development Munich, Germany
Data Management Solutions
forum.subscriber@iiug.org wrote on 26.11.2004 20:06:29:
> we are using the onmode -c block/unblock commands to synchronize the db
and
> using the onbar -r -e (external backup tools) to recover it.
>
> we did many recovery test, with log and without logs, most of the time
> successfully except for these 4 times that I got the corruption.
>
> External backup tools are not supported by Informix, but onmode and
onbar
> cmds exist for this type of backup......>
>
>
> -----Original Message-----
> From: Robert Roussey
>
[mailto:IMCEAEX-_O=SPIRITAIR_OU=RESCT_CN=RECIPIENTS_CN=ROBERTRO@SpiritAir.co
> m]
> Sent: Friday, November 26, 2004 1:55 PM
> To: Lavoie, Diane; ids@iiug.org
> Subject: RE: backup strategy using HDS - shadow image, true copy [3789]
>
>
>
> Neither of those will work because they totally ignore the Informix
> timestamp (used for all backups and restores) that exists on every data
page
> and in the system catalog. The only way those utilities would work is
if
> you shut down informix and did them.
>
>
> Bob Roussey
> Spirit Airlines
> Informix/Unix Administration
> Phone: 586.741.8991
> e-mail: RobertRo@SpiritAir.com
>
> -----Original Message-----
> From: forum.subscriber@iiug.org [ mailto:forum.subscriber@iiug.org
> <mailto:forum.subscriber@iiug.org> ] On Behalf Of Lavoie, Diane
> Sent: Friday, November 26, 2004 11:28 AM
> To: ids@iiug.org
> Subject: backup strategy using HDS - shadow image, true copy [3789]
>
> Hi,
>
> We are presently testing shadow imange and true copy, as a backup
solution
> for our Informix database.
>
> This will replace the Informix Onbar backups. While performing some
recovery
>
> testing using this new
> method, I got corrupted database.
>
> Anybody using shadow image or true copy as database backup solution? Any
> comments will be much appreciated.
>
> Regards
>
>
>
>
Hi,
We are using 7.31FD2,FC6 and 9.31.
The corruption was either when changing the status to Online, we lost one
mirror of the logdbs or
when applying the logs, one chunkd was offline.
Diane
-----Original Message-----
From: Martin Fuerderer [mailto:MARTINFU@de.ibm.com]
Sent: Monday, November 29, 2004 4:39 AM
To: Lavoie, Diane
Cc: forum.subscriber@iiug.org; ids@iiug.org
Subject: RE: backup strategy using HDS - shadow image, true copy [3791]
Hi,
the description of what you're doing sounds about right.
(BTW: we call it "External Backup and Restore".)
What version of IDS are you using ?
Can you describe the corruptions and the circumstances
where they occurred in more detail ?
Regards,
Martin
--
Martin Fuerderer
IBM Informix Development Munich, Germany
Data Management Solutions
forum.subscriber@iiug.org wrote on 26.11.2004 20:06:29:
> we are using the onmode -c block/unblock commands to synchronize the db
and
> using the onbar -r -e (external backup tools) to recover it.
>
> we did many recovery test, with log and without logs, most of the time
> successfully except for these 4 times that I got the corruption.
>
> External backup tools are not supported by Informix, but onmode and
onbar
> cmds exist for this type of backup......>
>
>
> -----Original Message-----
> From: Robert Roussey
>
[mailto:IMCEAEX-_O=SPIRITAIR_OU=RESCT_CN=RECIPIENTS_CN=ROBERTRO@SpiritAir.co
> m]
> Sent: Friday, November 26, 2004 1:55 PM
> To: Lavoie, Diane; ids@iiug.org
> Subject: RE: backup strategy using HDS - shadow image, true copy [3789]
>
>
>
> Neither of those will work because they totally ignore the Informix
> timestamp (used for all backups and restores) that exists on every data
page
> and in the system catalog. The only way those utilities would work is
if
> you shut down informix and did them.
>
>
> Bob Roussey
> Spirit Airlines
> Informix/Unix Administration
> Phone: 586.741.8991
> e-mail: RobertRo@SpiritAir.com
>
> -----Original Message-----
> From: forum.subscriber@iiug.org [ mailto:forum.subscriber@iiug.org
> <mailto:forum.subscriber@iiug.org> ] On Behalf Of Lavoie, Diane
> Sent: Friday, November 26, 2004 11:28 AM
> To: ids@iiug.org
> Subject: backup strategy using HDS - shadow image, true copy [3789]
>
> Hi,
>
> We are presently testing shadow imange and true copy, as a backup
solution
> for our Informix database.
>
> This will replace the Informix Onbar backups. While performing some
recovery
>
> testing using this new
> method, I got corrupted database.
>
> Anybody using shadow image or true copy as database backup solution? Any
> comments will be much appreciated.
>
> Regards
>
>
>
>
Hi,
things to watch when using external backup and restore:
- always backup all chunks of the system within one
bracket of "onmode -c block/unblock" commands.
Partial backups are not supported (for restore).
- Therefore during backup, all dbspaces and chunks
must be online (i.e. may not be down).
- Also backup mirror chunks.
- If a (yet undetected) corruption exists during backup,
it will be restored as well and then cause a problem
when applying logs. Possibly use "oncheck" to detect
a problem before backup, or do a test-restore (on a
different system) to verify that a backup is good.
- Always restore the complete backup, including the
mirror chunks. Partial (cold) external restores followed
by warm external restore are not recommended/supported
with external backup and restore.
Note:
- There's no easy way to verify correctness/completeness
of a backup as the backup is done by external means
and ON-Bar cannot check it.
- It is possible to optimize with mirror chunks by backing
up only one "copy" of a mirrored pair of chunks.
But you are responsible for:
- restoring the backup to both, primary and mirror chunk,
- during backup to pick the correct chunk (and not a chunk
that may be down). I.e. if primary chunk is down you need
to backup the mirror chunk instead and vice versa.
- Such "mirror-optimized" backup can be tricky and error prone.
Make sure you have well-tested scripts that reliably select
chunks for backup and correctly restore them.
Following these recommendations should avoid corruptions
or similar problems with external backup and restore.
Apart from this, a problem can be a down BLOBSpace chunk
when a log file is backed up (where this log file contains log
records that reference a BLOB in the down BLOBSpace). Older
versions of IDS may not report the problem prominently.
But during log restore and recovery (after external physical
restore) there will be a problem with applying these log records,
possibly resulting in inconsistencies. However, this is a general
problem, not just with external backup and restore.
Regards,
Martin
--
Martin Fuerderer
IBM Informix Development Munich, Germany
Data Management Solutions
forum.subscriber@iiug.org wrote on 29.11.2004 18:23:57:
> Hi,
>
> We are using 7.31FD2,FC6 and 9.31.
>
> The corruption was either when changing the status to Online, we lost
one
> mirror of the logdbs or
> when applying the logs, one chunkd was offline.
>
> Diane
>
> -----Original Message-----
> From: Martin Fuerderer [mailto:MARTINFU@de.ibm.com]
> Sent: Monday, November 29, 2004 4:39 AM
> To: Lavoie, Diane
> Cc: forum.subscriber@iiug.org; ids@iiug.org
> Subject: RE: backup strategy using HDS - shadow image, true copy [3791]
>
>
> Hi,
>
> the description of what you're doing sounds about right.
> (BTW: we call it "External Backup and Restore".)
>
> What version of IDS are you using ?
> Can you describe the corruptions and the circumstances
> where they occurred in more detail ?
>
> Regards,
> Martin
> --
> Martin Fuerderer
> IBM Informix Development Munich, Germany
> Data Management Solutions
>
> forum.subscriber@iiug.org wrote on 26.11.2004 20:06:29:
>
> > we are using the onmode -c block/unblock commands to synchronize the
db
> and
> > using the onbar -r -e (external backup tools) to recover it.
> >
> > we did many recovery test, with log and without logs, most of the time
> > successfully except for these 4 times that I got the corruption.
> >
> > External backup tools are not supported by Informix, but onmode and
> onbar
> > cmds exist for this type of backup......> >
> >
> >
> > -----Original Message-----
> > From: Robert Roussey
> >
>
[mailto:IMCEAEX-_O=SPIRITAIR_OU=RESCT_CN=RECIPIENTS_CN=ROBERTRO@SpiritAir.co
> > m]
> > Sent: Friday, November 26, 2004 1:55 PM
> > To: Lavoie, Diane; ids@iiug.org
> > Subject: RE: backup strategy using HDS - shadow image, true copy
[3789]
> >
> >
> >
> > Neither of those will work because they totally ignore the Informix
> > timestamp (used for all backups and restores) that exists on every
data
> page
> > and in the system catalog. The only way those utilities would work is
> if
> > you shut down informix and did them.
> >
> >
> > Bob Roussey
> > Spirit Airlines
> > Informix/Unix Administration
> > Phone: 586.741.8991
> > e-mail: RobertRo@SpiritAir.com
> >
> > -----Original Message-----
> > From: forum.subscriber@iiug.org [ mailto:forum.subscriber@iiug.org
> > <mailto:forum.subscriber@iiug.org> ] On Behalf Of Lavoie, Diane
> > Sent: Friday, November 26, 2004 11:28 AM
> > To: ids@iiug.org
> > Subject: backup strategy using HDS - shadow image, true copy [3789]
> >
> > Hi,
> >
> > We are presently testing shadow imange and true copy, as a backup
> solution
> > for our Informix database.
> >
> > This will replace the Informix Onbar backups. While performing some
> recovery
> >
> > testing using this new
> > method, I got corrupted database.
> >
> > Anybody using shadow image or true copy as database backup solution?
Any
>
> > comments will be much appreciated.
> >
> > Regards
> >
> >
> >
> >
>