Nenad,
As Andrew Kerber mentioned, there is a data replication extension called
DRBD which extends PCS for disaster resilience; his blog post (HERE
<https://dbakerber.wordpress.com/2019/03/15/oracle-cluster-with-drbd-pacemaker-and-corosync/>)
is awesome. His final comment on HA with DR using PCS/DRBD sums
everything nicely: /Note that this is not true HA. It takes about 10
minutes for failover to occur and for Oracle to start on the second
node. If you need true HA, you will need to spend the money required
for a commercial solution./
Customers running Oracle who geo-replicate for disaster resiliency use
DataGuard. MAX AVAILABILITY is also capable of *meeting* RPO=0 in most
circumstances, although it is not a guarantee as with MAX PROTECTION.
For customers with applications with less-strict RTO, then there are
more cost-effective options such as Azure NetApp Files cross-region
replication and Azure VM Backup Recovery Vault, each of which can be
used to capture snapshot backups in a vault for provision-upon-failover,
providing a tradeoff between RTO and cost; running a costly "hot"
standby for low RTO, or provisioning the standby environment at time of
failure for higher RTO.
Personally, I haven't considered Oracle clusterware (CRS) without RAC
for DR/HA purposes. I don't believe that Oracle CRS has any licensing,
so it would be "free" like PCS, while of course both require support.
But cost (or lack of it) is beside the point. Oracle CRS doesn't have
the worldwide community of support that PCS has, and CRS doesn't (appear
to) have the library of resource and fencing agents that PCS has. Last,
CRS is tied to Oracle database, while PCS is not, providing HA not only
with databases but also basic network services like DNS, NTP, NFS, POP,
SMTP, IMAP, etc.
For what it is worth, I have posted a bash script to Github HERE
<https://github.com/tigormanmsft/ora-pcs/>which fully automates the
creation of a Pacemaker/Corosync cluster running Oracle in Azure; it
requires the Azure CLI (downloadable HERE
<https://docs.microsoft.com/en-us/cli/azure/install-azure-cli>) to
create the vnets, VMs, and other stuff in Azure. The script takes about
45 mins to run, mostly because of the time spent in DBCA and doing "yum
update -y" on the OEL images with Oracle database preloaded in the Azure
Marketplace. If you don't have a subscription with enough rights to run
all of the Azure CLI commands, the scripts still represent "living
documentation" if you like reading commented shell script. :)
Also, for what it is worth, I have posted a similar script HERE
<https://github.com/tigormanmsft/dg-fsfo/>which fully automates the
creation of an Oracle DataGuard FSFO cluster separated across
availability zones within Azure. Same thing; it takes about 40 mins to
run to completion, if you have permissions.
Hope this helps...
-Tim
On 5/17/2021 10:44 PM, Noveljic Nenad wrote:
Hi Tim,
Thank you for this information.
How do your customers who use PCS replicate data for DR: ASM mirroring or some storage/OS replication feature?
Do your customers configure MAX PROTECTION mode to satisfy the RPO=0 requirement with data guard?
Have you considered using Clusterware without RAC with the ASM mirroring for DR/HA purposes?
Best regards,
Nenad
*From:*Tim Gorman <tim.evdbt@xxxxxxxxx>
*Sent:* Montag, 17. Mai 2021 20:11
*To:* Noveljic Nenad <nenad.noveljic@xxxxxxxxxxxx>; ORACLE-L (oracle-l@xxxxxxxxxxxxx) <oracle-l@xxxxxxxxxxxxx>
*Subject:* Re: Linux VM Failover
Nenad,
I have Azure customers using Pacemaker/Corosync (PCS) HA clusters on Linux (i.e. SUSE, RHEL, OEL) for Oracle databases in Azure. Out of the box, PCS supports other databases such as MySQL, SAP HANA, SAP ASE (Sybase), IBM DB2 LUW, etc; pretty much anything.
PCS is the open-source descendent of the older proprietary-UNIX HA clustering packages such as IBM HACMP on AIX, HP ServiceGuard on HP-UX, Sun HA on Solaris, and Veritas Clustering on several OS platforms. So, the reason people used those proprietary HA clustering technologies is likely the reasons PCS is used with Linux today?
As for my Azure customers, they prefer the same HA clustering method across all applications and databases, which is not an unusual viewpoint when HA and DR are the responsibility of the infrastructure team, as opposed to being the responsibility of each of the database/application administration teams. For Oracle-based applications with RPO=0 and RTO < 30 seconds, DataGuard is the preference for its disaster resilience across geographies and its support for true "rolling upgrades" of database changes using DBMS_ROLLING. Some customers claim that DataGuard is "too expensive" because it requires double the storage, but that view quickly fades when compared to the additional US$23000/core licensing and US$5060/core support fees for RAC.
With Oracle's power play of not supporting RAC on non-Oracle clouds, people are increasingly recognizing RAC as an overly expensive one-trick pony for HA.
Hope this helps,
-Tim
On 5/17/2021 9:45 AM, Noveljic Nenad wrote:
Does anyone use OS cluster for failing over Linux VMs with Oracle
databases to another node?
If so:
1. What were your reasons against Oracle Clusterware?
2. What cluster/Linux variant do you use?
Best regards,
Nenad
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