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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242
votes
27answers
58k 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 ...
106
votes
15answers
86k 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 ...
25
votes
15answers
18k 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 ...
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 ...
13
votes
2answers
8k views

LVS vs HAProxy, which should I choose?

I am looking for a solution to load balancing and failover strategy, mainly for big web applications. We have many services to be balanced, such as web, MySQL, and many other HTTP or TCP based ...
9
votes
6answers
7k views

How do you automate failover on EC2?

Of the folks managing their own clusters (i.e. not using/paying for Amazon Autoscale, Rightscale, Scalr, etc.), how are you managing your instances on EC2 and handling (e.g.) failover? I'm wondering ...
8
votes
5answers
624 views

Hot spare host vs cold spare host?

We have several hosts where we have an identical hot spare host, which is patched and updated so it is very close to have to same software and config. In case of failure the network cable is switched ...
8
votes
11answers
9k views

good failover / high availability solutions for linux?

I have several cases where I need applications to be migrated from one server to another in the event of a failure (server hang or crash). On solaris we do this with VCS (Veritas Cluster Server). ...
8
votes
3answers
15k 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; ...
8
votes
3answers
796 views

Global high availability setup question

I own and operate visualwebsiteoptimizer.com/. The app provides a code snippet which my customers insert in their websites to track certain metrics. Since the code snippet is external JavaScript (at ...
8
votes
2answers
3k views

How browsers handle multiple IPs

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 ...
8
votes
7answers
4k 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
7answers
7k views

Linux equivalent of pfsync+carp for failover firewall/routing

I'm currently using a linux box to handle my firewall/NAT using iptables. It has two NICs, one link to a LAN switch, one to our egress Internet provider. I'm looking at upgrade this box to two boxes ...
7
votes
2answers
670 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 ...
7
votes
5answers
2k views

Local to Remote Webserver Failover

Short and sweet, I don't suppose you'll need more detail than this: We host our website on an in-house webserver. A catastrophe has and will happen again where communication from the web into/out ...
7
votes
4answers
701 views

What is the most effective way to setup a linux web server for manual failover

I currently administer a small web server running ubuntu linux with apache, mysql, and ssh. I'm backing it up using rsync to another server, but I'm backing it up to a /backup directory. I'd like to ...
6
votes
6answers
13k 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). ...
6
votes
2answers
2k views

Magento hosting on a budget

I have to do a setup for Magento. My constraint is primarily ease of setup and fault tolerance/fail over. Furthermore costs are an issue. I have three identical physical servers to get the job done. ...
6
votes
2answers
2k views

Hadoop disk fail, what do you do?

I would like to know about your strategies on what to do when one of the Hadoop server disk fails. Let's say, I have multiple (>15) Hadoop servers and 1 namenode, and one from 6 disks on slaves ...
6
votes
2answers
1k views

What happens if my WHS boot disk or other hardware component failes?

I was boasting to some of my co-workers yesterday that my Windows Home Server (WHS) had my entire home network backed up and that is my recovery plan for a failed hard disk on one of the home ...
6
votes
6answers
5k views

Cluster failover and strange gratuitous arp behavior

I am experiencing a strange Windows 2008R2 cluster related issue that is bothering me. I feel that I have come close as to what the issue is, but still don't fully understand what is happening. I ...
6
votes
1answer
4k views

MySQL: Pacemaker cannot start the failed master as a new slave?

pacemaker-1.0.12-1 corosync-1.2.7-1.1 I'm going to setup failover for MySQL replication (1 master and 1 slave) follow this guide: ...
6
votes
1answer
3k views

Pacemaker Active/Active haproxy load balancing

I am using Haproxy to load balance replicated mysql master servers. I am also using Heartbeat and Pacemaker for Active/Active ip failover with two virtual ips on the two load balancers for web server ...
5
votes
2answers
9k 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 ...
5
votes
5answers
3k 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 ...
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 ...
5
votes
5answers
1k views

Websockets Server with Fault-Tolerance and Durable Message Store

I am starting to experiment with websockets. Does anyone know of a websockets server (open source or paid) that provides a durable store of the websocket "channel"? All of the examples that I have ...
5
votes
2answers
890 views

Is rsync a good candidate for failover implementation (very large dataset)?

I have a large a set of data (+100 GB) which can be stored into files. Most of the files would be in the 5k-50k range (80%), then 50k - 500k (15%) and >500k (5%). The maximum expected size of a file ...
5
votes
6answers
3k views

Ubuntu failover from Ethernet-to-ADSL-modem to USB 3G dongle

I have an internet connected Ubuntu server, connected by Ethernet to a residential ADSL line. This is adequate, most of the time, but I can't rely upon the ADSL link to be as reliable as I'd like. ...
5
votes
4answers
2k views

Providing high availability and failover using MySQL on EC2

I would like to have a highly-available MySQL system, with automatic failover, running on Amazon EC2 instances. The standard approach to solving this is problem Heartbeat + DRBD, but I've found a lot ...
5
votes
3answers
2k views

High Availability for SSL Web Site

One of our web server clusters serves a moderate number of busy e-commerce applications. At present, each site lives on a specific web server and has a hot-spare copy mirrored to another web server ...
5
votes
2answers
945 views

ISC DHCP+BIND with failover and dynamic updates, can the secondary bind update DDNS?

I'm setting up a failover system for DHCP and DDNS. The software being used are ISC BIND and ISC DHCP, running on Ubuntu 10.04 LTS. serverA runs DNS01 and DHCP01, serverB runs DNS02 and DHCP02. DHCP ...
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
443 views

How to handle IP's with manual failover?

I have two identical storage hosts where the master is the only one the users can access. If the master fails, then I want to manually change the DHCP address, so instead of master points to ...
4
votes
9answers
12k 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 ...
4
votes
5answers
5k 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
3answers
519 views

Cheap clustering for SQL server

Does anyone know of a way to simulate a clustered SQL server solution? We obviously don't want to spend a lot of money prototyping the idea, but we have quite a few PCs available. I was just wondering ...
4
votes
2answers
5k views

How good is failover of the iSCSI target on a two-node linux san?

I'm evaluating the possibility to use two off the shelf servers to build a cheap iSCSI redundant SAN. The idea is to run linux, pacemaker, and an iSCSI target - something like the SAN Active-Passive ...
4
votes
1answer
170 views

DRBD for HA Server in Small Office Questions

Backround: We are in need of a HA server in a small office environment and are looking at DRBD to provide it. We only have about 100GB that needs to be on the HA server and server load will be ...
4
votes
6answers
3k views

Redundant Load Balancers for Windows-based Web Servers?

I'm having some trouble trying to figure out the technical details of the below design; specifically in the area of the redundant load-balancers. The web servers are running Windows Server 2003 R2 64 ...
4
votes
2answers
5k views

NIC Active/Passive bonding with priority

I will configure a bond of three NIC's. I want to define which one will be first used and which NIC will be used as the second and third NIC when failover is done. Is this possible? Thanks
4
votes
2answers
2k 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 ...
4
votes
3answers
2k views

Should the SAN (Dell MD3200) management port be on the same subnet/VLAN as the failover cluster private subnet/VLAN?

So, I'm getting a bit confused here. I have a Dell MD3200 SAN with dual controllers. Each controller has an Ethernet management port that connects to a switch. Together the two controllers connect to ...
4
votes
4answers
3k 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 ...
4
votes
2answers
744 views

synchronizing storage servers

we have a storage server, with currently an amount of about 20TB of media files which we want to synchronize with a second storage server, for backup and fail-over. the facts are: we're storing ...
4
votes
1answer
2k views

Additional Domain Controller Failover and Failback

I have installed a DC – Let’s call it as DC1 I have installed a Second DC using (Additional Domain Controller for an existing domain controller option) – Let’s call it as DC2 Can anyone tell me: 1) ...
4
votes
1answer
1k views

DNS Failover with multiple Nginx load balancers

Our application is hosted on EC2, however because the nature of the app, it requires extremely high availability. We have an image of the app running on Linode as a failover. However, doing a DNS ...
4
votes
1answer
64 views

Blackberry Outage: How can I PIN a large number of users?

We lost power due to the hurricane and need to notify BES users that services will be restored soon. How can I extract all BES users and send them a notification message? Also how do I alter the ...
4
votes
2answers
843 views

Failover Internet connection?

In my Linux server i have three network cards. The eth0 card is connected to ISP1, the eth1 card is connected to LAN and the eth3 card is connected to ISP2. What i want to do is to automatically use ...
4
votes
1answer
537 views

Hyper-V R2 can't add a teamed NIC as External Network

I have a Dell PowerEdge R710 running Windows Server 2008 R2 Datacenter and which was part of a Hyper-V Failover Cluster. It has 8x Broadcom BCM5709C NICs and three are teamed together to be my ...