If you run ASM, it needs access to raw devices. You can provide either PVs or LVs for that purpose. Now, if you ignore licensing, a fully active/active cluster for ASM is the best approach. ASM is always active and controlling disks and you can manage data distribution with whatever tools ASM provides. PowerHA doesn't have to explicitly support ASM in any way, so I am not sure exactly what you need support for?
Second option is to use ASM on PVs. AIX, LVM or PowerHA will in that case not have anything to do with the disks. PowerHA will only control start and stop of ASM on the node as required. There will be no disks in the RG. This is a good way too, to manage ASM, and you let ASM take full responsibility for data and distribution. We have a policy of renaming all raw device PVs in AIX, so that operators can easily identify them (we use HDS storage, and we rename them to asm_<LDEV>_<SERIAL> so we can easily identify the disks and where they come from, and since this info is in the ODM it is easy to script it). Use native storage methods to mirror/distribute data, or ASM to do the same as far as it supports it.
Last option is to use raw LVs and let PowerHA manage the VGs as part of the RG. It works well enough, but you need to map each LV to one PV to get the expected performance based on ASM policy of treating a volume as one IO and availability domain. You gain the possibility to manage storage through AIX LVM, but generally I would not recommend it as it is more operationally demanding. Can be mitigated through automated monitoring of LV mapping and sync status. You also need to take care of how to switch. Concurrent VG, and control where it is read/write, risk of split brain and cluster problems due to infrastructure outages or errors, problems coordinating between DBA and OS operators, depending how you are organised...
PowerHA as such isn't too picky, unless you want to use PowerHA and Hyperswap or other specific PowerHA to storage integrations. You can easily add DLPAR, Storage Management commands and automation and other features, but I would recommend keeping it simple.
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Morten Torstensen
TietoEVRY
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Original Message:
Sent: Wed September 22, 2021 03:39 PM
From: Jakub Pacowski
Subject: ASM on PowerHA
Mackey,
maybe I wasn't clear enough. It's not about mixing RAC with PowerHA. It's about using ASM with PowerHA instead of JFS2 and LVM. I don't want to use both cluster managers. I'm just not sure if PowerHA with ASM (no RAC) is supported configuration.
Btw. I've also got one client that had 4-node PowerHA cluster with 2x RAC clusters - one site 2-nodes RAC Cluster, second site 2-node RAC clusters all in 4x node PowerHA cluster. Idea was to use PowerHA for replication management between sites and local RAC cluster for high availability. What's more activation of resource group was set up with dynamic resources (DLPAR on CPU). Idea was to limit Oracle licenses required, but I'm not sure if savings were worth making the configuration much more complex.
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Jakub Pacowski
Original Message:
Sent: Wed September 22, 2021 10:27 AM
From: Mackey Morgan
Subject: ASM on PowerHA
Jakub, it has been a VERY long time since I have worked with Oracle RAC on IBM Power. However, my strong impression from my dim recollection is that trying to mix two HA managers, Oracle RAC and PowerHA, in the same cluster is not recommended. IIRC, RAC handles moving the virtual IP (or re-points the Oracle client?) from one node to another (and yea, I'm pretty sure two nodes is a minimum) and monitoring/starting/restarting the app (Oracle). And ASM manages the redundancy of block storage in far greater detail than possible with the PowerHA management of AIX LVM.
On a hunch, is this someone's bright idea for avoiding payment for additional Oracle licenses??
At any rate, my advice would be to reach out to Oracle SMEs with experience with RAC cluster configuration and management (and licensing ;-). And leave off trying to serve two masters ;-).
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Mackey Morgan
Original Message:
Sent: Mon September 20, 2021 03:42 AM
From: Jakub Pacowski
Subject: ASM on PowerHA
Hello All,
I haven't seen any new threads for a long time, but hope someone is still checking the group.
I'm struggling to find confirmation that Oracle ASM is supported with PowerHA. Can someone point me to right direction?
J.
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Jakub Pacowski
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