[IQUG] IQ 16 Multiplex shared disk cluster

Antonian, Vahe vahe.antonian.2 at credit-suisse.com
Thu Aug 24 06:10:53 MST 2017


In an IQ Multiplex environment, comprised of multiple nodes, the cluster version of a Logical Volume Manager (CLVM) must be used so that each node can access the disks. This will cost more and also add to infrastructure complexity.

Vahe Antonian
Database IB Ops Service
+1 212 538 1642 (*106 1642)
From: Baker, Chris [mailto:c.baker at sap.com]
Sent: Thursday, August 24, 2017 9:06 AM
To: Antonian, Vahe (MLEA 42); iqug at iqug.org
Subject: RE: IQ 16 Multiplex shared disk cluster

You don't need anything.  Not sure where you are reading about a clustered LVM as a definite requirement (please provide the link).  For some platforms, we do now support some cluster/shared LVM solutions, per the docs, but in reality, IQ MPX was designed to not need anything at all.  This avoids the performance degradations implicit in a shared RW LVM, and the cost.

All you really need is RW access to the same raw partitions mounted to each node from a SAN.  IQ manages all the locking internally to prevent concurrent access to the same block by multiple nodes (something that is then redundant with a shared RW LVM, but at an added cost).

The raw partitions on the SAN are mounted as devices under /dev as block devices, then converted to /dev/raw character devices with ownership of the raw devices changed to be RW only by the invoker of the IQ server.

I suggest using symlinks in the .db directory to point to the /dev/raw devices to allow ease of portability and also makes creating the multiplex easier, especially in cases where you may have other block or raw devices mounted in different places on different nodes.

Attached are examples of the rules you need to convert the block devices to character raw devices under RHEL.  IMHO this is much more preferable than using a rawservice as the rules fire before services, allowing you to start IQ as a service (daemon) if you desire.


Chris Baker | Database Engineering Evangelist | CERT | PI HANA Platform Data Management | SAP
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From: iqug-bounces at iqug.org<mailto:iqug-bounces at iqug.org> [mailto:iqug-bounces at iqug.org] On Behalf Of Antonian, Vahe
Sent: Thursday, August 24, 2017 8:12 AM
To: iqug at iqug.org<mailto:iqug at iqug.org>
Subject: [IQUG] IQ 16 Multiplex shared disk cluster

Curious what folks are using as their shared disk cluster software for IQ 16 Multiplex on Redhat (RHEL 6). SAP online whitepapers and knowledgebase articles have little to no detail and simply state that a clustered LVM is needed for the nodes to share the devices.


Vahe Antonian
Information Technology | Database IB Ops Service, MLEA 42
One Madison Avenue | New York NY 10010 | Americas
Phone +1 212 538 1642
vahe.antonian.2 at credit-suisse.com<mailto:vahe.antonian.2 at credit-suisse.com> | www.credit-suisse.com<http://www.credit-suisse.com>

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