Browsing articles tagged with "highavailability - 15/16 - Admins Goodies"
Aug 10, 2011
tom

Looking for a DNS Hosting provider with automatic failover and role switching

I need to set up automatic failover with two SQL Server Instances and mirroring. There are several DNS hosters (such as DNS Made Easy and Netriplex) out there providing automatic failover. The are monitoring your server instances every minute and if primary goes down the domain name resolves to the secondary server’s IP. My problem is that I also need to switch server roles when in case of an automatic failover and this is not […]

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Aug 10, 2011
tom

Snapshot/rollback in Kvm using DRBD

I want to use the HA on a virtual machine on two server using KVM/libvirt. I placed the image on a partition using DRBD. I’m using the qcow2 format and i’m taking the snapshot, using virsh snapshot-create vm I think that it saves it in the qcow2 image. But it creates the xml doc in the /var/lib/libvirt/qemu/snapshot/vm/1306756846.xml. When an host crushes, the other server is not able to see the snapshot unless i copy the […]

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Aug 9, 2011
tom

Predict the number of primaries after a split-brain situation

I am trying to avoid a split brain situation using automatic split brain recovery policies explained at http://www.drbd.org/users-guide/s-configure-split-brain-behavior.html How to predict which condition we are involved in? How to predict the number of primaries after split brain? Is it all accidental? How many nodes do you have? More than two? Anyway I found the following setup to be the best to recover from split-brains: after-sb-0pri: discard-zero-changes after-sb-1pri: discard-secondary after-sb-2pri: disconnect So first we throw away […]

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Aug 9, 2011
tom

Alternatives to Heartbeat, Pacemaker and CoroSync?

Are there any major alternatives for automatic failover on Linux besides the typical Heartbeat/Pacemaker/CoroSync combinations? In particular, I’m setting up failover on EC2 instances, which only supports unicast – no multicast or broadcast. I’m specifically trying to handle the few pieces of software we have which don’t already have automatic failover and don’t support multi-master environments. This includes tools like HAProxy and Solr. I have Heartbeat+Pacemaker working, but I’m not thrilled with it. Here are […]

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Aug 9, 2011
tom

Veritas Cluster Server for HA for regular user processes

In the past I have used Veritas Cluster Server for HA clusters of Sybase and other databases at large financial institutions. Now I am going to have locally written processes that could benefit from some similar behavior. e.g. “fail onto this machine if this process fails” We will have VCS in the environment for various databases, so the overall skill set is not an issue; but this specific aspect. Have you used VCS for custom […]

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Aug 9, 2011
tom

LDAP (389 Directory Service) and Pacemaker with Multi-Master

I’m trying to setup a pair of LDAP servers running 389 (formerly Fedora DS) in high availability using Pacemaker with a floating IP. In addition, 389 supports multi-master replication, where all changes on one node are automatically replicated on one or more other nodes. I’m fairly close to having everything working. Failover works just fine. And multi-master replication works fine. However, my current Pacemaker config stops the directory service on the non-active node. Which means […]

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Aug 9, 2011
tom

High Availability without IP Failover?

Are there strategies or techniques to create HA environment when IP failover isn’t available? I’m reading a guide at Linode’s library which describes exactly what I want to do, but I’m not sure my current VPS host supports IP failover. IP failover using hearbeat/pacemaker requires the ability to move an IP address between nodes. If your VPS provider locks you into a single IP address, then that isn’t the route you want to take. You’ll […]

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Aug 9, 2011
tom

Pinging Virtual IP for Linux HA cluster from a different subnet does not work

I have setup a Linux cluster with Corosync/Pacemaker, and the two cluster nodes are within the same subnet sharing a virtual IP. For machines within the same subnet, they can ping the virtual IP “135.121.192.104” successfully. However, if I tried to ping the virtual IP “135.121.192.104” from the machine from a different subnet, then it does not respond to my ping. The other machines resides on the subnet “135.121.196.x”. On my machines, I have the […]

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Aug 9, 2011
tom

High Availability MySQL question

So I’m currently testing a new DB topology before moving it into a production environment, and I’ve run into a rather odd problem. The current setup is as follows: 5 server instances. 2 are MySQL DBs in Master/Master . 2 are slaves that point to a virtual IP(VIP), which currently points to one of those masters. The 5th server is load balancing between the slaves using MySQL proxy. So the idea is to have all […]

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Aug 9, 2011
tom

Synchronous Multimaster Replication postgresql pgpool 2

We would like to build a system of two Postgresql 8.4 servers, with pgpool 2 in front that will make all writes go to both systems. In the event of a failure on one of the nodes, it will degrade and pgpool will direct all writes at the remaining node. From there we can manually re-sync everything and bring it all back up. Im currently doing some testing to this effect, and noticing some interesting […]

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