HDR vs. SRDF

I'm setting up a high availability/DR environment for a 9.40 database on AIX. The service provider wants me to use EMC's SRDF to replicate/clone data at the disk level vs. using HDR. Has anyone successfully used such a technology for this purpose? I prefer to use Informix native components for this, but may have not choice. Thanks in advance.

We currently use the SRDF to take a snapshot of the database 3 times a day during the online day. In the SRDF script we start the copies once they complete we issue a "onmode -c block" then break the mirror and issue a "onmode -c unblock" the whole process of the break leaves the instance locked for around 3 seconds. We then are able to use this copy for testing or backups as needed. This has worked fine for 6+ years. There is an EMC doc on this named ?Integrating EMC TimeFinder and SRDF Software with Informix Dynamic Server" *** Please note the new address and phone number below. Bruce Simms Data Base Services TALX Corporation 2330 Ball St. Louis, MO 63146 Phone (314) 214-7703 FAX (314) 983-3238 bsimms@talx.com -----Original Message----- From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of GARY PRICE Sent: Wednesday, January 03, 2007 3:28 PM To: ids@iiug.org Subject: HDR vs. SRDF [8084] I'm setting up a high availability/DR environment for a 9.40 database on AIX. The service provider wants me to use EMC's SRDF to replicate/clone data at the disk level vs. using HDR. Has anyone successfully used such a technology for this purpose? I prefer to use Informix native components for this, but may have not choice. Thanks in advance. ************************************************************************ ******* Forum Note: Use "Reply" to post a response in the discussion forum.

Bruce Simms said: > > We currently use the SRDF to take a snapshot of the database 3 times a > day during the online day. In the SRDF script we start the copies once > they complete we issue a "onmode -c block" then break the mirror and > issue a "onmode -c unblock" the whole process of the break leaves the > instance locked for around 3 seconds. We then are able to use this copy > for testing or backups as needed. This has worked fine for 6+ years. > There is an EMC doc on this named ?Integrating EMC TimeFinder and SRDF > Software with Informix Dynamic Server" Failover wouldn't be as quick as HDR, though. -- Bye now, Obnoxio "I don't read newspapers anymore except the local rag which I do weekly to cheer myself trying to see if anyone I hate has been stabbed." -- Horribilis XVI -- This message has been scanned for viruses and dangerous content by OpenProtect(http://www.openprotect.com), and is believed to be clean.

We also do SANP exactly as Bruce mentioned but personally I am not very convenciencd. Think of a situation where a transaction was in progress doing insert etc. when we blocked server and did a SNAP. Now for some reason that transaction has been rolled back. Now DB restored from SNAP copy, will have those records but in fact prod may not be having those records. You can see a thread on this in IIUG. Cheers. ----- Original Message ---- From: Bruce Simms <BSimms@talx.com> To: ids@iiug.org Sent: Thursday, January 4, 2007 8:47:36 AM Subject: RE: HDR vs. SRDF [8089] We currently use the SRDF to take a snapshot of the database 3 times a day during the online day. In the SRDF script we start the copies once they complete we issue a "onmode -c block" then break the mirror and issue a "onmode -c unblock" the whole process of the break leaves the instance locked for around 3 seconds. We then are able to use this copy for testing or backups as needed. This has worked fine for 6+ years. There is an EMC doc on this named ?Integrating EMC TimeFinder and SRDF Software with Informix Dynamic Server" *** Please note the new address and phone number below. Bruce Simms Data Base Services TALX Corporation 2330 Ball St. Louis, MO 63146 Phone (314) 214-7703 FAX (314) 983-3238 bsimms@talx.com -----Original Message----- From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of GARY PRICE Sent: Wednesday, January 03, 2007 3:28 PM To: ids@iiug.org Subject: HDR vs. SRDF [8084] I'm setting up a high availability/DR environment for a 9.40 database on AIX. The service provider wants me to use EMC's SRDF to replicate/clone data at the disk level vs. using HDR. Has anyone successfully used such a technology for this purpose? I prefer to use Informix native components for this, but may have not choice. Thanks in advance. ************************************************************************ ******* Forum Note: Use "Reply" to post a response in the discussion forum. ******************************************************************************* Forum Note: Use "Reply" to post a response in the discussion forum. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

Hi, I can't see the problem with transaction rollback. If you start your DB copy without logical restore all open transactions get rolled back anyway. And if you start your DB copy with logical restore you will reach the same state as your source DB has (if you have all logical logs). But there is another point: What is the main purpose of your replicated database instance? For building testing environments or checking the production database SRDF (or similar technics, e.g. disk mirror split) are a great thing. And you don't have any impact on your production system (except a small performance loss for the time you take the snapshot). With HDR I remember a lot of threads talking about indexes, consistency and blocking, right? But if you want a failover solution, SRDF might not be the best technic. If you do only a few snapshots a day you have the problem of rolling forward to production state (may take a long time / you may have problems to access and apply the logs). When doing the SRDF snapshot your database copy is not consistent - if something happens at that time you might not be able to start the copied database. If you do 'continous' SRDF (always mirror on disk level) the risk of getting an inconsistent copy might even be worse - unless you use some kind of 'sync copy' which usually costs a lot of performance. Second a continous SRDF doesn't help you against logical corruptions (user error or writes of bad blocks). What do we do? We use SRDF (BCV mirror split as HP calls it) for (Level-0) backup and for building test environments (system copy). We have a almost synced mirror (Continous Access as HP calls it) for failover - that mirroring doesn't use synced writes, but preserves the order of writes and theoretically that should give a consistent copy. We have used HDR for copying/moving database instances, too. But we had sometimes errors with the HDR itself. And I worry that HDR might have impacts on large high performance databases. And if you do some data reorganization (without logging) you have to rebuild your HDR environment. Discussions are welcome. Regards, Andreas Kutsche > ------------------------------------------- SPAR Oesterreichische Warenhandels-AG Hauptzentrale Europastrasse 3 A - 5015 Salzburg Tel: +43 662 4470 24223 Mobile: +43 664 6259575 E-Mail: Andreas.KUTSCHE@spar.at Internet: http://www.spar.at Wichtiger Hinweis: Der Inhalt dieser E-Mail kann vertrauliche und rechtlich geschützte Informationen, insbesondere Betriebs- oder Geschäftsgeheimnisse, enthalten, zu deren Geheimhaltung der Empfänger verpflichtet ist. Die Informationen in dieser E-Mail sind ausschließlich für den Adressaten bestimmt. Sollten Sie die E-Mail irrtümlich erhalten haben so ersuchen wir Sie, die Nachricht von Ihrem System zu löschen und sich mit uns in Verbindung zu setzen. Über das Internet versandte E-Mails können leicht manipuliert oder unter fremdem Namen erstellt werden. 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We therefore do not accept legal liability for the information contained in this communication. The contents of the e-mail are only legally binding if they have been confirmed and signed by us in writing. If, in spite of our using Antivirus protection software, a virus may have penetrated your system through the sending of this e-mail, we do not accept liability for any damage that may possibly arise as a result of this. We trust that you appreciate our position. ------------------------------------------- -----Ursprüngliche Nachricht----- > Von: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org]Im Auftrag von > H.G > Gesendet: Donnerstag, 04. Jänner 2007 00:19 > An: ids@iiug.org > Betreff: Re: HDR vs. SRDF [8093] > > > > We also do SANP exactly as Bruce mentioned but personally I > am not very > convenciencd. Think of a situation where a transaction was in > progress doing > insert etc. when we blocked server and did a SNAP. Now for > some reason that > transaction has been rolled back. Now DB restored from SNAP > copy, will have > those records but in fact prod may not be having those > records. You can see a > thread on this in IIUG. > > Cheers. > > ----- Original Message ---- > From: Bruce Simms <BSimms@talx.com> > To: ids@iiug.org > Sent: Thursday, January 4, 2007 8:47:36 AM > Subject: RE: HDR vs. SRDF [8089] > > We currently use the SRDF to take a snapshot of the database > 3 times a > day during the online day. In the SRDF script we start the > copies once > they complete we issue a "onmode -c block" then break the mirror and > issue a "onmode -c unblock" the whole process of the break leaves the > instance locked for around 3 seconds. We then are able to use > this copy > for testing or backups as needed. This has worked fine for 6+ years. > There is an EMC doc on this named ?Integrating EMC TimeFinder > and SRDF > Software with Informix Dynamic Server" > > *** Please note the new address and phone number below. > > Bruce Simms > Data Base Services > TALX Corporation > 2330 Ball > St. Louis, MO 63146 > > Phone (314) 214-7703 > FAX (314) 983-3238 > bsimms@talx.com > > -----Original Message----- > From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of > GARY PRICE > Sent: Wednesday, January 03, 2007 3:28 PM > To: ids@iiug.org > Subject: HDR vs. SRDF [8084] > > I'm setting up a high availability/DR environment for a 9.40 > database on > AIX. > The service provider wants me to use EMC's SRDF to > replicate/clone data > at the > disk level vs. using HDR. Has anyone successfully used such a > technology > for > this purpose? I prefer to use Informix native components for > this, but > may > have not choice. > > Thanks in advance. > > ************************************************************** > ********** > ******* > Forum Note: Use "Reply" to post a response in the discussion forum. > > > ************************************************************** > ***************** > Forum Note: Use "Reply" to post a response in the discussion forum. > > __________________

Thanks much for your reply. I went to EMC's website and, despite quite a bit of searching, could not locate the document you mention. Do you per chance have a link, or better yet, a copy I could get via email? Thanks again for your help.