In computing, failover is automatic switching to a redundant or standby computer server, system, or network upon the failure or abnormal termination of the previously active application, server, system, or network. Failover and switchover are essentially the same operation, except that failover is ...

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143
votes
16answers
121k views

Why is DNS failover not recommended?

From reading, it seems like DNS failover is not recommended just because DNS wasn't designed for it. But if you have two webservers on different subnets hosting redundant content, what other methods ...
11
votes
2answers
6k views

How browsers handle multiple IPs [closed]

Can someone direct me to information on exact browsers behavior when browser gets multiple A records for a given hostname (say ip1 and ip2), and one of them is not accessible. I interested in EXACT ...
4
votes
5answers
6k views

How can I automaticaly change the DNS A record to point my site to a secondary server in case of a failure?

My hosting is charging me a $50/month fee to put my servers on the same VLAN so that I create a cluster using the Network Load Balancing feature. I'm really not needing split the load between the ...
4
votes
2answers
540 views

How to create a high-availability application server?

I am working with some hardware units which uses mobile Internet to communicate to my application server. Initially, the hardware had a hard-coded IP address (load balancer) in the hardware for ...
14
votes
2answers
27k views

nginx automatic failover load balancing

I'm using nginx and NginxHttpUpstreamModule for loadbalancing. My config is very simple: upstream lb { server 127.0.0.1:8081; server 127.0.0.1:8082; } server { listen 89; ...
11
votes
3answers
16k views

How to setup HAProxy with failover?

I understand that, to get failover on an HAProxy load balancing setup, you need two machines running HAproxy (and route it to several webserver instances). But in this case, say abcd.com, how do we ...
1
vote
3answers
8k views

Is it possible to make redundancy on HAProxy server?

I am going to use HAProxy as a load balancer that will balance requests on 3 application servers. But what if balancer server (HAProxy) fails at some point? I was thinking of cloning the first ...
5
votes
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 ...
5
votes
5answers
5k views

Many ISP's is block port 25, how do I choose an alternative port?

I am building an application that will be acting as a combined MUA/MTA on different networks. However, many of the networks are with ISP's that block port 25 for SMTP. Therefore I would also like to ...
3
votes
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'...
5
votes
4answers
3k views

Apache Failover and Load Balancing

I am working for a small finance firm as a Web Application Developer. Our company has an interal website coded in PHP and running on Apache. Recently our server went down and the website was down for ...
4
votes
9answers
15k views

Best solution for Multi-WAN failover (inside & out)? [closed]

Looking for a way to setup 2 ISPs in failover mode, for both incoming & outgoing traffic, for our small (<100 devices) network. The leading contender for now seems to be the Peplink Balance ...
3
votes
1answer
727 views

How could dynamic DNS work if DNS updates take hours to propagate?

Simple Failover markets itself as: continuously monitors your servers to find out which are up and which are down, and then it dynamically updates your DNS records accordingly so that your ...
3
votes
1answer
3k views

Redis sentinel + HAProxy failover

I am looking to implement a HA redis implementation using Master-Slave redis servers. The web servers will connect to these through an HAProxy instance installed on each box. The situation is easy ...
1
vote
2answers
874 views

“Simple” Failover to a Geographically Separated Server?

I've been reading about DNS failovers and a bunch of other technical terms however I'm a bit of a newbie in this so it all sounds Greek to me. Basically here's what I just need: I have two shared ...
1
vote
1answer
3k views

iSCSI / SAN / Cluster / multiple NICs failover

Got a problem with NIC failover with iSCSI. Setup: A server with 3 NICs. One NIC is local network, other 2 are SAN. Using Microsoft iSCSI Initiator. A managed network switch. A QNAP SAN, connected ...
274
votes
27answers
61k views

100% uptime for a web application

We received an interesting "requirement" from a client today. They want 100% uptime with off-site failover on a web application. From our web application's viewpoint, this isn't an issue. It was ...
25
votes
15answers
19k views

Cheapest iSCSI SAN for Windows 2008/SQL Server clustering?

Are there any production-quality iSCSI SANs suitable for use with Windows Server 2008/SQL Server for failover clustering? So far, I've only seen Dell's MD3000i, and HP's MSA 2000 (2012i), which both ...
4
votes
10answers
7k views

Is it possible to merge multiple internet connections?

I have two internet connections at my place but the faster one is actually unreliable. :( One is a broadband modem connected to PC via ethernet. The other one is a USB modem. I would want to run ...
15
votes
5answers
2k 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 ...
9
votes
7answers
39k views

Why are my HyperV VM's randomly losing connectivity?

I have a strange intermittent connectivity problem happening about once every two weeks. First my configuration: I am running a HyperV failover cluster with two physical hosts (node01 and node02). ...
8
votes
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-...
4
votes
4answers
14k views

Link bonding across multiple switches?

I've read up a little bit on bonding nics with ifenslave; what I'm having trouble understanding is whether there is special configuration needed in order to split the bonds across two switches. For ...
7
votes
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 ...
2
votes
1answer
9k views

How to make iptables ALLOW rule for multicast?

I have two servers that uses ucarp as failover. On each server eth1:1 is reserved for ucarp's keepalive connection. ucarp uses the destination IP as multicast address 224.0.0.18. On ucarp master ...
1
vote
2answers
4k views

How to configure failover for JBoss AS 5?

I am currently an intern in my company. My boss basically wants me to perform a failover from a JBoss AS to another just for a proof of concept. Load balancing is not required as i am only required to ...
5
votes
1answer
2k views

DNS Round-robin failover and load balancing

Having read all of the questions and answers (1 2 3 and so on) on here relating to DNS load balancing, and Round-robin DNS, there's still a number of unanswered questions.. Large companies, and I'm ...
4
votes
2answers
3k views

Multiple LDAP servers with mod_authn_alias: failover not working when the first LDAP is down?

I've been trying to setup redundant LDAP servers with Apache 2.2.3. /etc/httpd/conf.d/authn_alias.conf <AuthnProviderAlias ldap master> AuthLDAPURL ldap://192.168.5.148:389/dc=domain,dc=...
4
votes
4answers
185 views

Achieving Five Nines

I am building a web application where uptime is key. I understand that 100% uptime is not realistic but I would like to achieve five nines. I'm unsure as to the most prudent way to accomplish this. ...
3
votes
3answers
295 views

How to recover from switch failure? [closed]

Suppose there is only one switch within a system and it is connected to a bunch of machines to form a network. If this switch goes down, the entire network goes down. Chances of this happening are ...
3
votes
2answers
4k views

Browser-based DNS failover using multiple A records

It has recently come to my attention that setting up multiple A records for a hostname can be used not only for round-robin load-balancing but also for automatic failover. So I tried testing it: I ...
2
votes
1answer
766 views

Failover/redundant SSH

I have an SSH server where multiple clients SSH in to maintain a bunch of port forwards. What I want to do is, if the server goes down, have the clients automatically connect to the next server. The ...
2
votes
4answers
10k 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 ...
1
vote
2answers
7k 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 ...
1
vote
2answers
1k views

How do I do IP Failover for my Public IP address with Linux HA

I did a lot of experiment with heartbeat, corosync and pacemaker for IP FailOver which I have to do with Public IP. I did more than one ip failover(VIPs) with two nodes, also with three nodes BUT ...
1
vote
1answer
927 views

DC/DNS failover with global/common DNS roundrobin

I think I am getting lost in network failover land. I am trying to set up a Windows Domain Controller and DNS, while providing resilients and failover. I have two Domain Controllers and DNS servers. ...
4
votes
3answers
4k views

Access files located on the underlying filesystem of an NFS mountpoint

Perhaps this is an odd request, but it's the opposite of the question detailed at: Is it possible to view the contents of an underlying NFS mount without unmounting the NFS content? I have an ...
4
votes
6answers
4k views

How do I set up failover for a single web server using two ISPs?

I have one web server and two WAN connections (1 cable, 1 DSL). DNS is run offsite, and points to the IP address assigned by one of the ISPs. How can I have the second connection take over when the ...
3
votes
1answer
3k views

Configuring Secondary DNS to Work if Primary is down (Bind)

I have a master slave DNS server setup with bind. The secondary DNS server is working correctly and resolves any queries sent to it. However, when the primary DNS is down, it seems that the secondary ...
3
votes
1answer
2k views

Heartbeat Pacemaker 3 node/ip failover

I have setup two node active/active ip failover with heartbeat and pacemaker following the link at zivtech on the two load balancers for the backend web servers. Two LBs has public ip each which is ...
2
votes
1answer
536 views

Intermittent unavailability of an instance in a failover cluster while a standby node is offline in a SQL Server 2008 failover cluster

I've got a small failover cluster that I run for the websites my company has. During a RAM upgrade of the standby server, our websites started to show errors about not being able to access the ...
2
votes
2answers
657 views

SSD redundancy via HDD

Is there a way to guarantee redundancy to an SSD using an HDD? Raid 1 is the best choice to guarantee redundancy in HDDs, but SSDs are too expensive to guarantee redundancy via RAID. If I was to ...
2
votes
3answers
2k views

Using a low TTL to help prevent extended periods of downtime

Is it feasible to set my domain's TTL to a very low value (a couple of minutes) so that, if my main host goes down for an extended period of time, I can update the DNS records in my main host to point ...
2
votes
1answer
1k views

Best failover strategy for e-mail servers on AWS to ensure high availability

We have our e-mail server hosted on AWS. Last week Amazon had a failure in their East Coast region which brought down our server along with many others. We now want to implement a failover strategy ...
1
vote
2answers
3k views

Failover between 2 catalyst 2960s

We have two catalyst 2960s and four linux servers that we would like to connect to both switches (each server having one link to each switch.) Ideally, we are looking for seamless failover in case a ...
1
vote
3answers
543 views

Firewall or other solution for automatic fail-over to a second server?

Assume a situation like this: Server 1 - FreeBSD, Apache -- serves all web traffic Server 2 - FreeBSD, Apache -- just sits there idling Is that an easy way to set things up so that if Server 1 ...
1
vote
1answer
41 views

Enable HTTPS with CNAME Apache

I have two apache servers, both of which hostnames are primary.domain.com and secondary.domain.com The Primary server will rsync and mirror all files to Secondary server as a backup. I am trying to ...
0
votes
2answers
2k views

Failover pacemaker cluster with two network interfaces?

So, i have two test servers in one vlan. srv1 eth1 10.10.10.11 eth2 10.20.10.11 srv2 eth1 10.10.10.12 eth2 10.20.10.12 Cluster VIP - 10.10.10.100 Corosync config with two interfaces: ...
0
votes
1answer
544 views

Cisco ASA failover can't ping gateway

I'm currently trying to set up a failover network for my Cisco ASA 55x0 using the SLA traking. I have the "outside" interface (network 89.x.x.48/29) and the "outside2" interface (network 192.168.70.0/...
0
votes
1answer
380 views

redirect to a static page on another web server when main web server is down

We have a single IIS web server in house that when it goes down we would like to redirect traffic to another web server and display a message that the web site is down. I have been all over the net ...