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#Mirroring

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Mirroring is an InterSystems technology for High Availability, Disaster Recovery and Database Backup and OLAP solutions.

Documentation.

Hi, this post was initially written for Caché. In June 2023, I finally updated it for IRIS. If you are revisiting the post since then, the only real change is substituting Caché for IRIS! I also updated the links for IRIS documentation and fixed a few typos and grammatical errors. Enjoy :)

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Mirroring 101

Caché mirroring is a reliable, inexpensive, and easy to implement high availability and disaster recovery solution for Caché and Ensemble-based applications. Mirroring provides automatic failover under a broad range of planned and unplanned outage scenarios, with application recovery time typically limited to seconds. Logical data replication eliminates storage as a single point of failure and a source of data corruption. Upgrades can be executed with little or no downtime.

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In this article, we’ll build a highly available IRIS configuration using Kubernetes Deployments with distributed persistent storage instead of the “traditional” IRIS mirror pair. This deployment would be able to tolerate infrastructure-related failures, such as node, storage and Availability Zone failures. The described approach greatly reduces the complexity of the deployment at the expense of slightly extended RTO.

Open Exchange app
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ISCAgent is automatically installed with Cache, runs as a service and can be configured to
start with the system. This is fine – but the complication comes when this is on VCS clusters with
Mirroring on. When installing a Single Instance of Cache in a Cluster, point number 2. Says “Create
a link from /usr/local/etc/cachesys to the shared disk. This forces the Caché registry and all
supporting files to be stored on the shared disk resource you have configured as part of the
service group.”

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Article
· Aug 4, 2021 3m read
IRIS Mirror in the cloud (AWS)

I have been working on redesigning a Health Connect production which runs on a mirrored instance of Healthshare 2019. We were told to take advantage of containers. We got to work on IRIS 2020.1 and split the database part from the Interoperability part. We had the IRIS mirror running on EC2 instances and used containers to run IRIS interoperability application. Eventually we decided to run the data tier in containers as well.

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Question
· Mar 23, 2017
problem with Mirroring

Hello, Thanks in advance for all replies. I have been practicing setting up mirroring between two development servers in preparation for mirroring our production server in a few weeks. I started by setting the servers up with minimum security which worked easily, then I set it up in lock down mode again without any issues. Now I am setting it up in lockdown mode with encryption and this one is testing me. I have everything setup but my async dr member cannot connect to the primary.

from cconsole.log

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++ Update: August 1, 2018

The use of the InterSystems Virtual IP (VIP) address built-in to Caché database mirroring has certain limitations. In particular, it can only be used when mirror members reside the same network subnet. When multiple data centers are used, network subnets are not often “stretched” beyond the physical data center due to added network complexity (more detailed discussion here). For similar reasons, Virtual IP is often not usable when the database is hosted in the cloud.

Network traffic management appliances such as load balancers (physical or virtual) can be used to achieve the same level of transparency, presenting a single address to the client applications or devices. The network traffic manager automatically redirects clients to the current mirror primary’s real IP address. The automation is intended to meet the needs of both HA failover and DR promotion following a disaster.

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Question
· Aug 2, 2016
Use of $ZUTIL(49) is deprecated

Hi all,

I'm using $ZUTIL(49) to get information of the databases I want to add to a mirror. This information is passed to ##class(SYS.Mirror).CatchupDB(plstPathDatabases) in order to Catchup all databases addes to a Mirror.

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I've created a scheduled task that dumps HL7 messages to flat files. It uses the OutputToLibraryStream() method of EnsLib.HL7.Message. I'd like to be able to run it on a mirror member host whether it's primary or backup.

When run against a database that's mounted read-only, it works fine. However, when I attempt to run it against a mirror backup database, I get the following error:

#5002: Cache error: <PROTECT>%LoadData+7^EnsLib.HL7.Message.1

Tracing that back to the source, I find:

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Question
· Aug 4, 2021
Azure Mirroring - VIP

Has anyone firstly got VIP working for mirroring in Azure? We are pretty sure that this won't work but I wanted to verify it.

Has anyone used the Azure Load balancer to act as a Virtual IP and if so was a application gateway required.

Interested to know your experiences in getting this working.

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Question
· Oct 30, 2016
ISCAgent debug

Good day!
Is there an opportunity to debug the ISCAgent behaviour (in Linux)? ISCAgent uses /etc/iscagent/iscagent.conf as configuration file, but in docs I've found a description only for two parameters (port number and interface - http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...). Other parameters I can see by running /usr/local/etc/cachesys/ISCAgentCtrl status:

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Hi,

Can a Cache Mirror be used in the cloud ? (ie stand up a Primary and Backup member instances in a High Availability Cache Mirroring configuration)

I'm investigating the validity of this configuration, because I was of the understanding that this may not possible due to these cloud servers not (typically) having fixed ip addresses, which interferes with the Virtual IP settings for the mirror set.

Is this correct, and if there are workarounds (like Load Balancing ?) can I have details on how this should be configured ?

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I am new to setting up a mirror environment....

We will have a Arbiter, Two Failover members (A,B), and a Async (DR) member (C). I have the two failover members in sync and are configured for Arbiter Control.

My question is about the Async member, when I initially set it up I pointed it to the mirror on the primary node A.

Is that correct?

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In this post, I am going to detail how to set up a mirror using SSL, including generating the certificates and keys via the Public Key Infrastructure built in to Caché. The goal of this is to take you from new installations to a working mirror with SSL, including a primary, backup, and DR async member, along with a mirrored database. I will not go into security recommendations or restricting access to the files. This is meant to just simply get a mirror up and running.

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Does anyone have experience with installing the Arbiter Container using Podman instead of Docker in a Red Hat environment? I was able to pull down the docker image, but unsure what are the next steps as I am confused on how to start the container using Podman and ensure the parameters are set appropriately? Does anyone have the steps that I should take? Should I go through the WRC? Does the WRC have experience using Podman?

Or should I just install the ISC Agent instead of using the Container?

Please and thanks,

Scott Roth

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I had a question about using ZSTART, ZSTOP, and ZMIRROR.

  • If we use them and it is not correct, does it mess up with any of the existing functionality?
  • So, if I create a ZSTART with a simple command of starting the %JDBC Server will that mess up anything existing in the Startup sequence?
  • Is ZSTART, ZSTOP, and ZMIRROR just an extension of the existing functionality, or does it alter how the built in functionality runs?
  • Should we tread lightly in the use of them?
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Question
· Aug 18, 2016
Read only Async mirror setup

I have setup an async reporting mirror member with Read only access. My problem is that if I try to do any sql reporting against that data I am getting errors. I am sure that this is because the DB is read only, but I had assumed that setting up a reporting mirror would handle this.

I there a setting or mapping I am missing?

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When I create a TASK on the Primary mirror member and Try to create the same TASK in the backup mirror member, It Gives me CSP Application error.

The TASK gets created in the Primary node without any errors and When creating in the Backup node it prompts the error.

It happens is IRIS and I didn't face this in CACHE.

Finally what I did is export the TASK in Primary and Imported in Backup.

Is this a feature of IRIS?

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Hey Developers,

We're pleased to invite you to join the next InterSystems IRIS 2020.1 Tech Talk: DevOps on June 2nd at 10:00 AM EDT!

In this InterSystems IRIS 2020.1 Tech Talk, we focus on DevOps. We'll talk about InterSystems System Alerting and Monitoring, which offers unified cluster monitoring in a single pane for all your InterSystems IRIS instances. It is built on Prometheus and Grafana, two of the most respected open source offerings available.

Next, we'll dive into the InterSystems Kubernetes Operator, a special controller for Kubernetes that streamlines InterSystems IRIS deployments and management. It's the easiest way to deploy an InterSystems IRIS cluster on-prem or in the Cloud, and we'll show how you can configure mirroring, ECP, sharding and compute nodes, and automate it all.

Finally, we'll discuss how to speed test InterSystems IRIS using the open source Ingestion Speed Test. This tool is available on InterSystems Open Exchange for your own testing and benchmarking.

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Hello,

I work on deploying IRIS inside Docker container. I really like %Installer class can automate many steps. I want to establish an ECP connection to a mirror database and then define a remote database on the application server. I have already seen we can create local database and namespace in %Installer. What code is needed to establish ECP connection?

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Hello everyone!
Maybe someone will tell me what could be the reason for such messages in the message.log file

05/03/23-06:46:27:155 (6584) 0 [Utility.Event] [SYSTEM MONITOR] Mirror state: Member type = Failover, Status = Transition
05/03/23-06:46:27:350 (1620) 1 [Utility.Event] Failed InstanceLookup (agent probably not running): instance not found
05/03/23-06:46:27:351 (1620) 2 [Utility.Event] Failed to become either Primary or Backup at startup

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Article
· Nov 4, 2022 9m read
VIP in AWS

If you're running IRIS in a mirrored configuration for HA in AWS, the question of providing a Mirror VIP (Virtual IP) becomes relevant. Virtual IP offers a way for downstream systems to interact with IRIS using one IP address. Even when a failover happens, downstream systems can reconnect to the same IP address and continue working.

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Hello Everyone,

We currently have CSP application that runs under 2 servers(usually primary), and every month the server reboots for patching SERVER1(primary) in the morning and SERVER2(backup) at night.

Whenever the SERVER1 reboots SERVER2 behaves as primary and when SERVER1 comes back up it will act as backup server.

First Patching:

So, when SERVER1 is down, I need to start httpd service for SERVER2 and stop httpd service for SERVER1 (which is now backup server).

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