Mirroring

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In this post I show strategies for backing up Caché using External Backup with examples of integrating with snapshot based solutions. The majority of solutions I see today are deployed on Linux on VMware so a lot of the post shows how solutions integrate VMware snapshot technology as examples.

Last comment 16 November 2018
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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. 

Last comment 14 June 2018
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++Update: August 2, 2018

This article provides a reference architecture as a sample for providing robust performing and highly available applications based on InterSystems Technologies that are applicable to Caché, Ensemble, HealthShare, TrakCare, and associated embedded technologies such as DeepSee, iKnow, Zen and Zen Mojo.

Azure has two different deployment models for creating and working with resources: Azure Classic and Azure Resource Manager. The information detailed in this article is based on the Azure Resource Manager model (ARM).

Last comment 8 July 2016
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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.

Last comment 8 December 2018
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Context: 

mirrored configuration with one primary member and one async member (without failover/backup member)

Purpose:

replace the CACHE.DAT of a mirrored database on the primary member.

 Steps to follow:

Last comment 21 October 2016
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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.

Last comment 29 March 2017
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Mirror Outage Procedures

Caché mirroring is a reliable, inexpensive and easy to implement high availability and disaster recovery solution for Caché and Ensemble-based applications. This article provides an overview of recommended procedures for dealing with a variety of planned and unplanned mirror outage scenarios.

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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 InterSystems IRIS Data Platform. I did a similar post in the past for Caché, so feel free to check that out here if you are not running InterSystems IRIS. Much like the original, 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. Example screenshots are taken on a 2018.1.1 version of IRIS, so yours may look slightly different.

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Mirroring provides an admin capability to Stop Mirroring on this member, which causes a non-primary member to temporarily disconnect from the primary, stop dejournaling, etc.  While most system administrators may never need or use this function, some employ it for certain kinds of maintenance or other special cases.

Last answer 7 June 2016 Last comment 7 June 2016
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Hi, Community!

Please find the Developer Community video of the week: 

Upgrades - Minimizing Business Disruption

 

Last comment 20 July 2017
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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:

Last answer 3 November 2016 Last comment 7 November 2016
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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 ?

Last comment 10 March 2016
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I have a DR Mirror   with a WIJ that is 5 times as large as the Primary Failover member. My Read-Write Reporting mirror WIJs are the same size as the Primary.  I don't  know why the DR WIJ i so large and would like to shrink it to the same size as the others.  Any suggestions are welcome. Thanks!

Last answer 16 March 2019
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Hi guys

I've added a new mirrored failover member to an existing one.

They are both Arbiter controlled.

When I do Add database to mirror on the primary I'm always getting an error. Missing Mirrored database.

I followed everything in the documentation and always get the same error.

I've copied the CACHE.dat file after umounting the database on both servers. then mounted them.

Could you help me out?

 

Kind Regards

Last answer 4 March 2019
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InterSystems has corrected a defect that can result in data integrity problems in environments that use InterSystems mirroring in conjunction with parallel dejournaling. This problem exists for currently released Caché and Ensemble versions beginning with 2017.2 and for InterSystems IRIS Data Platform version 2018.1.

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Hi, would really appreciate your advice on how I can restart the mirror-monitor. I've followed the instructions and restarted the mirror monitor, and still the status seems to be down. Can you point me to some resource or steps that I can follow ?

I logged into %SYS terminal and restarted the mirror monitor and it says that it is running

Last answer 24 December 2018 Last comment 30 December 2018
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Hi All!

I asked previously about the DR server in the cloud but actually, I'm curious about the backup server to use as analytics server more than for recovery in DR case.

There is a recommended practice to use an async mirror as a server for BI (InterSystems Analytics, DeepSee)

The question is if I have PRIMARY in the cloud (AWS, Google, Azure, etc) "how far" should async mirror member be placed? Same cloud, same private cloud or it doesn't matter at all for analytics purposes?

Last answer 16 November 2018 Last comment 16 November 2018
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In System Administration | Configuration |  System Configuration | Journal Settings there is a check box for Freeze on error.

From reading the documentation, it sounds like the choice to freeze on error is one of system availability vs system integrity.

Curious to know whether Ensemble users choose to freeze on error or not.

If you have a best practice recommendation based upon your experience or knowledge, that would be helpful information too.

Last answer 5 June 2018 Last comment 4 June 2018
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Hi

I'm using this query "Config.MapMirror.List" To get information of the list of servers that are in the mirror system.

I'd like to know how can I know which of the list is the primary and which is the failover or async member.

Is there a way to do it with this query? Is there another query to get this info?

Thanks a lot

Last answer 7 May 2018 Last comment 8 May 2018
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Hi, Community! 

 Check a new session recording from Global Summit 2017:

Mirror, Mirror, Which Should I Choose?

 

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I have Ensemble/Healthshare running in a production environment which is setup with a mirror failover and an arbiter sitting between them.

In the event of a failover we have a number of connections that need stopping/monitoring and starting in a certain order.

Is there a programmatic way we can detect the failover and stop certain services and operations immediately and then start them up again in the required order, checking their connection state before starting the next connection.

Last comment 10 November 2017
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Is it possible to make the cache terminal available over a mirrored vip address for a healthshare mirrored environment? So that connecting to a terminal for a mirrored environment will always connect to the Live Node?

 

I'm looking to write a Powershell script to run against the system and need to connect to the Live Node in a mirrored setup. Is this possible or am I going to have to log onto each node to establish which is Live.  Or does this even matter?

Last answer 1 November 2017 Last comment 6 November 2017
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