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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51
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11answers
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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
3k 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 ...
3
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2answers
2k 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). ...
5
votes
4answers
5k 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 ...
14
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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 ...
7
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7answers
3k views

How to perform cron jobs failover?

Using two Debian servers, I need to setup a strong failover environment for cron jobs that can be only called on one server at a time. Moving a file in /etc/cron.d should do the trick, but is there ...
7
votes
4answers
7k 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
votes
3answers
3k 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 ...
2
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1answer
2k views

relation between heartbeat,openais,corosync

i am planning for high availability on lucid ubuntu, i started with drbd after a simple configuration on drbd I went to heartbeat and had a simple config on it too. on drbd official site a document ...
0
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1answer
59 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 ...
0
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3answers
340 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 ...
7
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4answers
5k 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 ...
2
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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 ...
9
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5answers
458 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 ...
3
votes
1answer
4k views

Keepalived for more than 20 virtual addresses

I have set up keepalived on two Debian machines for high availability, but I've run into the maximum number of virtual IP's I can assign to my vrrp_instance. How would I go about configuring and ...
15
votes
5answers
1k views

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 ...
11
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7answers
7k 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 ...
7
votes
2answers
584 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 ...
2
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1answer
4k 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 ...
2
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1answer
5k 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.
12
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3answers
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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 ...
2
votes
5answers
427 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 ...
1
vote
2answers
543 views

Is it possible to balance load between multiple Nginx load balancers without using a hardware load balancer?

I plan to balance load between my app servers using a separate Nginx server as a software load balancer. But actually, it's because a load balancer in front of the app servers allows me to update an ...
0
votes
2answers
1k views

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 ...
2
votes
4answers
502 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
2answers
595 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
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1answer
819 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
votes
1answer
193 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 ...
1
vote
0answers
111 views

High-availability for ZMQ traffic

We have a lot of incoming third-party ZMQ traffic (zmq.PULL on our side). We need to implement a high-availability solution for that traffic. At the very least, we need to be able to manually switch ...
1
vote
1answer
222 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 ...
4
votes
2answers
668 views

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 ...
4
votes
1answer
495 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 ...
3
votes
6answers
303 views

Wiki/CMS with synchronization? [closed]

We're looking into putting up a wiki or CMS for internal use by our IT department. One of the big things we want to use it for is disaster recovery procedures. Given that a disaster, such as a ...
2
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1answer
1k 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
2answers
1k 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
3answers
351 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 ...
1
vote
1answer
1k 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
6answers
955 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 ...
1
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4answers
884 views

Server CPU spikes suddenly and becomes unusuable - Tips to monitor/analyze this?

my server has been going down over the last 24-48 hours, CPU spikes from 15% to 100% and server becomes unusable and all my sites go down as a consequence of it. Any tips on how I could track what is ...
0
votes
2answers
393 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 ...
-1
votes
2answers
899 views

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 ...