High availability is an architectural consideration often involving degrees of redundancy to insure availability in case of system or component failure.

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Multiple data centers and HTTP traffic: DNS Round Robin is the ONLY way to assure instant fail-over?

Multiple A records pointing to the same domain seem to be used almost exclusively to implement DNS Round Robin as a cheap load balancing technique. The usual warning against DNS RR is that it is not ...
11
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8answers
4k views

Load balancing Apache on a budget?

I am trying to get my head around the concept of load balancing to ensure availability and redundancy to keep users happy when things go wrong, rather than load balancing for the sake of offering ...
5
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3answers
5k views

If DNS Failover is not recommended, what is?

As a followup question to his very popular question: Why is DNS failover not recommended?, I think it was agreed that DNS failover is not 100% reliable due to caching. However the highest voted ...
21
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7answers
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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 ...
3
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2answers
3k views

Keepalived over GRE tunnel for failover on VPS environment

I'm running an application on Linode. Their network does not support multicasting. Many tools used for failover (keepalived, spread/wackamole, hearbeat) require multicast to work (as far as I know). I'...
7
votes
4answers
8k views

Can Exchange 2010 high availability be achieved with only 2 servers?

In Exchange 2010, you can define Database Availability Groups and have your mailbox database(s) automatically replicated between multiple servers, and you can have mailbox server which are members of ...
5
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1answer
2k views

Should VMware HA Admission Control be enabled for small (2/3-host) clusters?

Take the following common scenario... A basic vSphere cluster running two or three hosts, shared storage and a token set of virtual machines under Essentials Plus or greater licensing. Should HA ...
0
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3answers
368 views

Connecting Linux system to switch from 2 interfaces

To get proper redundancy, we've installed 2 switches in our network and connected them to eachother. We now want to hook our servers to both switches. Since all servers have 2 ethernet ports, this ...
0
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1answer
66 views

Office network failover? [duplicate]

Possible Duplicate: What hardware do I need to add a backup internet connection? I have a office LAN providing internet access to several workstations. Each workstation is basically connected ...
9
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4answers
8k views

What exactly does Gluster do?

I've been playing with gluster for the last 2 days and been asking questions here and on their questions system. I really don't understand some of the stuff. I see people saying stuff like Set up ...
14
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8answers
16k views

Avoiding DNS timeouts when a dns server fails

We have a small datacenter with about a hundred hosts pointing to 3 internal dns servers (bind 9). Our problem comes when one of the internal dns servers becomes unavailable. At that point all the ...
3
votes
2answers
2k views

Load balancing / Failover for multiple VPS's set across different datacenters

I know many variants of this question has been asked already, but I still can't find a good answer to my needs. What I want to do is setup a few (2 at minimum) VPS's to host my web apps on. I'd like ...
10
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5answers
494 views

High server availabilty for a small business

After having a bit of scare with a server that wouldn't come up one morning, the higher ups have decided that the business needs a high availability / fail over setup. We have 5 main servers (4x ...
15
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5answers
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When my A web server gets unplugged, how do I automatically redirect all the users to my B web server in another city, and vice versa?

When my A web server gets unplugged, how do I automatically redirect all the users to my B web server in another city, and vice versa? A load-balancing switch does what I want, except I can't figure ...
8
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2answers
2k views

Multi-site high availability

We have a SaaS application that we need to be highly available. We already have an expensive, well-maintained Hyper-V failover cluster, but today the datacenter where we host that cluster had a five-...
7
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7answers
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Questions about single point of failure for small operations

If you can't afford or don't need a cluster or spare server waiting to come online in the event of a failure, it seems like you might split the services provided by one beefy server onto two less ...
3
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1answer
6k views

Heartbeat vs UCarp

Can anyone explain what is the major difference between Heartbeat and UCarp for IP fail-over scenarios? They both seem to provide this functionality, perhaps UCarp simpler to set-up? Thanks.
2
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1answer
8k views

My DAG has failed over, but Outlook clients won't connect

My company have two exchange 2010 server(Mail1 & Mail2) with DAG configuration. One day my Mail1 server down and the Mail2 auto take over! My question is now the end user can't access the mail2 ...
12
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3answers
1k views

The downsides of using nginx as a primary web server?

I've seen millions of websites using nginx as a proxifying webserver working together with Apache. But I've seen very few servers running nginx only as their default webserver. What are the main ...
7
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4answers
5k views

DNS Round Robin: Do browsers stick to one IP as long as it is online?

How do most browsers behave if they get multiple A-records from the DNS server? Do the stick to one IP as long as it is reachable (and only use another if the IP is down)? Or do they switch all the ...
7
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2answers
20k views

How to setup STONITH in a 2-node active/passive linux HA pacemaker cluster?

I am trying to setup an active/passive (2 nodes) Linux-HA cluster with corosync and pacemaker to hold a PostgreSQL-Database up and running. It works via DRBD and a service-ip. If node1 fails, node2 ...
6
votes
4answers
11k views

SonicWall “gotchas”?

We're looking to move away from PFSense and CARP to a pair of SonicWall NSA 24001 configured in Active/Passive for High Availability. I've never dealt with SonicWall before, so is there anything I ...
4
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2answers
2k views

Prevent HAProxy from toggling back from fallback to master

We have Redis master-slave setup, and we want to fallback to the slave once the master failed. But if it has failed it should never toggle back, even if the master is online again. Is this possible?
2
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5answers
467 views

Mysql high availability

I have a application that receives data from approximately 1000 different sources every couple of minutes. This data needs to be saved into a OSS database (most likely MySQL - but depending on answers ...
2
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1answer
2k views

ESXi Beacon Probing Limitation - Three Switches Required?

We are currently using Link Status Only for our NIC Teams on our VM hosts, but recently ran into an issue where one of our two switches had a memory error and stopped passing traffic. All of our VM ...
0
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2answers
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HA web cluster setup

I'm setting up a highly available web cluster, I'm planning to start out with 2 web servers connected to shared storage (perhaps via NFS). What's the best way of implementing this? Should the web ...
6
votes
3answers
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Is round-robin DNS a possible solution for high availability?

Let's say I have 2 IPs for a given domain (round-robin DNS). If one the IPs becomes unresponsive, will clients try to connect to the other IP? or they will just fail to establish comunication with the ...
2
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6answers
1k views

Will the OS crash if the system partition can't be access for a short period?

An operating system is installed in a virtual machine environment, such as VMWare or KVM. A network shared disk volume (e.g., iSCSI disk) is used as the OS system partition. Heavy traffic is running ...
2
votes
1answer
219 views

Multi-state MySQL master/slave pacemaker resource fails to launch on cluster nodes

Setup I'm setting up an HA cluster for a web application using two physical servers in a Corosync/Pacemaker managed cluster. After finding out I was heading the wrong way, I decided to use heartbeat'...
2
votes
4answers
9k views

DNS Round Robin: Multiple Nameservers VS Multiple A Records?

Note: This is a follow-up to my previous question regarding DNS Failover. The Goal: to make the client's web browser select the next available server if one is down instantly. I've read somewhere ...
2
votes
4answers
653 views

Solution for two-way file-system transparent solution

I need to implement some sort of HA setup where 2 servers need to be able to always be in sync, no matter on which one you write on. The DB part can be covered by a master-master replication setup. ...
2
votes
1answer
1k views

Highly Available Web Application (LAMP)

I work for a small company who provides a web application for thousands of users. Earlier this year they had one server hosted one company. We recently acquired another server in a different location ...
2
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1answer
241 views

What database is easy to maintain and manage in a cluster?

I'm looking for a database (DBMS) that is easy to scale out. I would like to have high availability so I need a multi-master cluster, where the data is replicated to two or more physical computers. I ...
2
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2answers
724 views

Does my BIND zone really provide redundancy and load balancing?

We have the following IP addresses (for example): 1.1.1.1 2.2.2.2 Each hosts the same website, but on a different server. We want to do some really simple load balancing by having web users visit a ...
2
votes
1answer
56 views

Get IP of node running a specific resource when demoting master nodes to slaves

Setup I am setting up a HA cluster for a web application with 2 nodes (2 physical servers): node1 (current master node) node2 (current slave node) Using Corosync & Pacemaker I was able to ...
1
vote
1answer
383 views

Monitoring pacemaker with url trigger external agent

I have a HA setup, which now the only resource configured is Heartbeat with Active/Passive Configuration. Both running Debian 7, 64-bit in the cloud. Now i want to trigger an URL with the information ...
1
vote
1answer
468 views

Advantage of Microsoft Cluster over Microsoft Network Load Balancer

Till recently, I assumed that Microsoft NLB worked at an OS/Machine level rather than an Application Level. i.e. the NLB just monitors heartbeats on the machine to check if machine is alive and then ...
1
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2answers
6k views

heartbeat: find out machine's status within a cluster?

I'm trying to do some heartbeat debugging. Is there a simple way to ask a machine whether it thinks it's part of a cluster, and whether it's the master or the slave? I've tried $ heartbeat -s ...
3
votes
1answer
2k views

How to lower Gluster FS down peer timeout / reduce down peer impact?

The setting: Two fresh CentOS 6.5 server with latest updates. Both have a fresh install of Gluster 3.5.2. What I did ( from the perspective of server 2, shared1 and shared2 are logical volumes ) : ...
2
votes
1answer
4k views

Where are Nagios Availability-Report files stored?

How to access Nagios Availability-Report files to retrieve "UP Time Percent" and so other information about Hosts and Services? I know It can be accessed through Nagios CGI but I want to use it on a ...
2
votes
1answer
118 views

How does systemd decide if a service is ok or not

This question is related to: reliable systemd service for autossh I have a service which uses type=simple. Here the systemd docs: Type=simple (default): systemd considers the service to be ...
2
votes
2answers
2k views

Network load balancing, efficience and limits?

I'm about to study about NLB on Windows Server 2003. It archives both of my interests now: scalability and high-availability. But I don't know about its power in production environment. Is NLB a ...
1
vote
1answer
1k views

Multimaster Keepalived Configuration (Virtual IP with Load Balancing)

Here are requirements: 1. High Availability 2. Load Balancing First configuration 1. Two linux servers have been configured with one static IP for each: 10.17.243.11, 10.17.243.12 2. Keepalived has ...
1
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1answer
2k views

MySQL cluster for Drupal?

We have a pretty busy site based on Drupal and I was thinking of introducing some form of clustering for HA and Load balancing. However, http://drupal.org/requirements says: Drupal supports MyISAM ...
1
vote
3answers
447 views

MySQL HA Solutions

I am evaluating the options to build MySQL HA and found the below solutions Percona XtraDB Cluster, Tungsten Replicator, and MySQL Cluster. Could you please help me to choose the best one with ...
0
votes
2answers
710 views

Tools to manage sql 2008 database mirroring?

We are going to be moving about 20 databases that live on a single instance of sql 2000 to a sql 2008 r2 environment with database mirroring. What I'm looking for is a tool or scripts that will help ...
0
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1answer
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iptable CLUSTERIP doesn't work

We have some requirements which explained here. We tried to satisfy them without any success as described. Here is the brief information: Here are requirements: High Availability Load Balancing ...
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2answers
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Simple IP load balancer for web service that runs on Windows XP or Windows 7 Professional?

I've a closed code application that needs to connect to a web service that needs to run on XPs or Windows 7 (desktop). The application can only connect to a single IP address. The application is low ...