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MaxDB high availability requirements questions

Former Member
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My company successfully has been using MaxDB (asd the database backend for things other than SAP) for the last five years, and I've been consistently impressed with its performance and stability. So far, we have been running it in a non-high availability configuration, but now we are looking to improve availability to an even higher level by looking into a high availability configuration.

Specifically, I have been looking into the hot standby setup, where a master and several standby instances run in a clustered environment with automatic failover. The system requirements for this at http://maxdb.sap.com/doc/7_6/d2/08d43f2dd44821e10000000a1550b0/content.htm mention that you need cluster software and a memory management system. I have access to a storage area network (though not managed by one of the products listed on this page), which hopefully should do for memory management, However, I am wondering about the cluster software requirement. The page lists an IBM AIX product as the only tested cluster software package. Does this mean that MaxDB hot standby configurations only run on AIX, or would using UltraMonkey (www.ultramonkey.org) or some similar HA solution for Linux also work in this capacity?

Any and all insight from people running hot standby configurations would be most appreciated.

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lbreddemann
Active Contributor
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Hi Johan,

if you're storage system is not listed in the documentation, than the hotstandby won't work as we rely on specific libraries from the storage system vendors to perform the hotstandby-failover.

See, this is not a generic approach but one that makes use of some very specific storage system features (e.g. parallel access to the same volume from different servers).

Anyhow - hotstandby is by far the most expensive cluster solution for MaxDB/liveCache. Are you sure, that you really need that?

What you should also keep in mind: running sessions will be rolled back and need to reconnect when a cluster switch is done.

With hotstandby you just shorten the time to have the db instance up and running again to the minimum. But you don't "rescue" running transactions.

If you're business can live with a failover time of several minutes (the time you need to startup your db instance) than you may implement such a standby cluster yourself - just remount the data/log-volumes to the other server and start the db.

KR Lars

Former Member
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Hi Lars,

Thanks for your prompt reply. I am aware that there are other solutions for increasing the availability of the database other than going all the way to a hot standby solution. However, I am trying to put together a solution that would obviate the need for going for something like Oracle RAC, meaning that I would need a true hot standby setup for which several minutes of down time on failure is not acceptable. I did check the standby database option in the documentation, but even if you automatically import log entries as frequently as possible, it seems that you'd still have to switch host names/IP addresses around to get the standby instance to take over as the active one and still be reachable by applications that access it by host and instance name (for instance over JDBC).

To confirm, am I correct in understanding your reply so that since the MaxDB hot standby solution relies on features that are specific to the cluster and memory management software packages listed in the documentation, there is no hope to get it to work (even unofficially) using other cluster software and SAN controllers? Unfortunately, we are not an AIX shop (though we do run Solaris extensively, so we're no strangers to Unix), which means that if so, unfortunately hot standby would be out of the question for us.

Thanks again for your insight!

lbreddemann
Active Contributor
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However, I am trying to put together a solution that would obviate the need for going for something like Oracle RAC, meaning that I would need a true hot standby setup for which several minutes of down time on failure is not acceptable.

Ok, basically you should enter a discussion with the consulting departement of SAP and your hardware vendor.

There is no option to "putting together" a HotStandby Cluster on your own.

BTW: MaxDB HotStandby and Oracle RAC are totally different types of cluster! They are not comparable in any way.

> To confirm, am I correct in understanding your reply so that since the MaxDB hot standby solution relies on features that are specific to the cluster and memory management software packages listed in the documentation, there is no hope to get it to work (even unofficially) using other cluster software and SAN controllers?

No - of course not! See, if you setup such a cluster, you want to make sure that it works correctly. This can only be done if you get the os/hw vendor and the software vendor together.

The same is true for Oracle RAC. As soon as you're using uncertified hardware etc. it might work somehow (e.g. RAC in VM installation), but nobody accepts responsibility for that setup.

>Unfortunately, we are not an AIX shop (though we do run Solaris extensively, so we're no strangers to Unix), which means that if so, unfortunately hot standby would be out of the question for us.

Sorry - I don't see that. What OS do you use? I said, that we rely on HW-specific libraries and these are available for several operation systems (although not all os supported by MaxDB are covered here).

KR Lars

Former Member
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Lars,

Thanks again for your prompt reply.

I was not implying that there were any architectural similarities whatsoever between MaxDB hot standby and Oracle RAC, I was merely stating that I was interested in building something that was similarly available in the face of node failures.

My comment about the AIX-specificness of the hot standby setup was due to the only cluster software listed as tested on the system requirements page at http://maxdb.sap.com/doc/7_6/d2/08d43f2dd44821e10000000a1550b0/content.htm is IBM High Availability Cluster Multiprocessing for AIX clustering software. For reference, we are running Solaris on SPARC and SLES on x86, with instances of SAN volumes being used on both platforms. While we're not running any clusters on either platform currently, we certainly would would not be averse to do doing so, and would in that case be working with our server vendor (for instance Sun) in setting it up.

Obviously I understand that nobody would accept formal responsibility for a setup that does not use the officially blessed components, that is not how any support game plays. Nor had I ever any intention of cobbling together a production system in this way. What I was initially interested in doing was to set up a proof of concept only. I would still use properly setup and configured cluster software and SAN controller solutions for this task. However, using any external consulting organization to additionally configure the database probably would be cost-prohibitive at this stage (also, we're not a current SAP customer).

If the list of officially tested cluster software and memory management products at http://maxdb.sap.com/doc/7_6/d2/08d43f2dd44821e10000000a1550b0/content.htm is incomplete, I would appreciate a pointer to a more exhaustive list. If there are indeed such products that can be used on Solaris or some Linux flavor I can still proceed in investigating the matter.

Thanks again,

Johan

markus_doehr2
Active Contributor
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For Sun Solaris (on x64) we are currently setting up a "test cluster" - it is supported for SAP application (and thus also for MaxDB):

Note 961762 - Sun Cluster support for SAP systems

There are a number of other agents available (and supported):

http://docs.sun.com/app/docs/coll/1574.2?l=de&q=maxdb+cluster

For Linux you can use Libelle (http://www.libelle.com/en/) or build "your own" using software like heartbeat. Cluster software is not supported by SAP but by the (hardware-)vendors.

Markus

Former Member
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Thanks! I will look into the link you provided, which does point to a path for Solaris that would be worth pursuing further. I was not aware of this resource existing before.

Thanks again,

Johan

Former Member
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Hello, I'm the cranky SysAdmin Johan has to put up with.

Is there a MaxDB HotStandby HW/SW Compatibility Matrix available from SAP?

If they are Storage Hardware Centric then such should be available without engaging SAP Consulting.

This project is in the early planning stages, given that the questions we're seeking answers to (not the details of our specific implementation) should be sufficiently available to allow us to determine a compatible environment without consuming consulting resources. Trudging through the SAP site looking for the basics of supported compatibilities has proven rather fruitless so far. None of the compatibility information seems readily available aside from what appears to be a footnote or two from the person(s) who tested it on AIX.

markus_doehr2
Active Contributor
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Check note 952783 - FAQ: MaxDB high availability

which has a very good explanation about the pros and cons of the different technologies.

The documentation states about the hardware:

EMC Symmetrix,

IBM TotalStorage Enterprise Storage Server (ESS),

IBM TotalStorage SAN Volume Controller (SVC)

which have been tested - but they don't exclude any other vendor. If you don't have one of them ask you vendor if he provides an interface to the libhss* library for the MaxDB.

The mentioned "AIX only" was referring to the tested cluster software. A setup documentation is e. g. available for HP-UX/MCSG: http://docs.hp.com/en/T2803-90011/T2803-90011.pdf (page 204).

Do you have hardware you want to use or do you implement everything "from scratch"?

Markus

Former Member
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For the SAN architecture we have Hitachi NSC55 (low end of the USP line) . For server, we'd be building to suit . Where might we find the 'Notes'your speaking of, I've not yet been able to find them via a search of the SAP website.

markus_doehr2
Active Contributor
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Check

http://service.sap.com/notes

Enter the mentioned note number in the field on the right hand side of the screen.

Another approach to search for that topic is:

Enter as component: BC-DB-SDB (or BC-DB-LVC for Livecache) and search for "ha" or "high availibility".

Markus