Redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe.

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MySQL Redundancy for High-Availability over the internet

I am testing out some infrastructure options before I start writing a web application. I would like to have two separate MySQL database servers at different physical locations, but if one of them ...
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1answer
3k views

Alternatives to Dell's mirrored SD card module for booting a small OS from flash?

Dell offers an add-on hardware card for some of their servers that provides a poor man's RAID1 between two SD cards (one card gets all the reads until it dies, writes are mirrored) for booting a ...
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1answer
647 views

Redundant Mailservers

We recently had a harddisk failure on our mail server (debian/postfix/courier) so I'm researching a way to build redundancy. The first way I found was to setup multiple mx Records in the DNS Server ...
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2answers
650 views

PowerConnect switches, Juniper firewalls and esx redundancy

Let me preface this question by saying that I am a developer and have basic knowledge of networking. My current job requires that I wear many hats. I am building out a DataCenter for our SaaS ...
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3answers
148 views

Multihomed email

Our primary MX record points to an external server which handles spam filtering, thereafter the mail is pushed to our internal mail server. The mail is never stored on the external server for longer ...
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5answers
5k views

Can you set a backup ip for your server in DNS?

Is there a way that the DNS protocol can natural hold a backup A type server address, like a backup name-server or mail server ? After googling i just got results on backup nameservers. If there isnt ...
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2answers
193 views

Two mirrored database servers, or one twice as powerful

I'm looking at setting up a seperate database server for one of my applications, the application currently runs on 3 servers; 1 frontend server and 2 application/database servers. But for performance ...
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2answers
163 views

Cloning Two Windows Servers

Basically I have a server running MSSQL, MYSQL, APACHE, IIS, ORACLE, PERL and other windows services. I am looking for some hardware solution that would allow me to clone a server on to a back up and ...
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2answers
250 views

Is it possible to do storage without RAID and unnecessary redundancy?

I'm building multiple storage nodes for Riak database. Each node contains 20-40 x 2TB drives. Riak replicates each save to 3 nodes so there I have redundancy. Now the question is that what's the best ...
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3answers
1k views

Is it possible to use mixed 110V / 208V power on a single server with dual power supplies?

Is it possible to run a dual power supply server with one PS plugged into 110V, and the other power supply plugged into 208V? We've asked the vendors and they say they've never tested it or some other ...
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3answers
6k views

How do you set up redundant servers?

To the sysadmins out there, I'm trying to get an idea about how you go about maintaining redundant servers for small projects. The modest number of servers in my mind is two, and three main essential ...
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1answer
158 views

Server redundancy or failsafe for small single office server

We run a local server in our office, and have a domain name pointed to it so we can test out sites we build. We also handle some image hosting for clients for emails. Since it's a single server, if ...
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3answers
337 views

Switch Redundancy for iSCSI

I am about to implement an iSCSI solution on our network. The thing that is bothering me though is that we are only using 1 switch from the SAN to node connections. Since each node has 2 NICs, is ...
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1answer
197 views

What steps can I take to ensure that my rails app on heroku isn't effected by another ec2 outage?

My app is a victim of the recent EC2 outage and is still offline. The outage has negatively effected my business and the relationship we have with our clients. I'm hosting the app on heroku with their ...
2
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1answer
412 views

Effects of having a rapid ARP flush

So the scenario is we have a web server at our colocation. In front of that web server are two SonicWalls and two L2 non-stacking managed switches. We're trying to find an efficient way to set up ...
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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 ...
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2answers
226 views

Placing UPS in front of STS; Connecting Dual PSU to same PDU

The site has 2 x 16A @ 230V, each server/SAN has dual PSU set up. Options: 1) [2 x 16A] ---> [1 x STS or ATS]----> [1 xUPS]---->[2 x PDU]----->[DUAL PSU] As can be seen the server is actually ...
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1answer
1k views

Windows Server 2008 multiple domain controllers?

We currently have a domain controller which has the profiles etc. for around 30 users. It is also the local DNS server and file server. As it's our only Domain Controller, if we ever have to restart ...
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2answers
377 views

IIS7: one domain, one IP, two servers, one as fallback

I would like to have a setup where I can tell any of two servers to be the "main"-server on a specific IP (for redundancy reasons). Both servers should be accessible at any given time but only one ...
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2answers
319 views

Cisco 6500 redundancy

Which of the following methods is best for redundancy in a Cisco 6500? Two Cisco 6500 chassis each with a single Sup720 and other modules. One Cisco 6500 chassis with two Sup720 modules and two of ...
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1answer
648 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 ...
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1answer
114 views

How to Add a Secondary Server, Correctly

Just wondering if a network of approximately 15 users has only 1 Server Running Windows 2003 and wanted to add a "secondary server" so that in the event the "primary" fails for any reason the ...
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2answers
156 views

Two hosting providers running simultaneously… possible / not possible? good practice / unnecessary?

For the sake of their reputation, I won't mention the names. But I'll just use: Business I worked for previously - ABC Web Dev Hosting company they used - XYZ Hosting I recently found out that XYZ ...
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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 ...
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7answers
5k views

Do you lose everything when you have a hard disk failure in a multi-hard disk LVM that does NOT use RAID?

I'm debating about using LVM for a media/file server because I would like to combine multiple physical hard disks into one volume. I do not wish to use any RAID in my LVM so my question is: If one ...
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3answers
5k 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 ...
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2answers
2k views

Failover/Load balancer for WHM/cPanel

I have a simple question for which I have not been able to find a simple answer. Here's the scenario: Server 1: WHM/cPanel with multiple accounts/dbs Server 2: WHM/cPanel with multiple accounts/dbs ...
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2answers
646 views

Howto create redundant network on server

I am in the situation where I have a number of CentOS Linux servers which all have two NIC interfaces. Currently one of these interfaces is used for internal communication, the other is used for ...
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3answers
495 views

IRC Services with failover support?

I run a single server (call it 'server A') IRC 'network', and thank to the generosity of some friends, I have been given a second server ('server B') that I can run an IRCd on in order to provide ...
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4answers
232 views

Question regarding uptime strategy for website

I'm working on a website where we need to have a good deal of uptime. Specially in the short bursts (15-day periods) that the website's events happen. The page is dead simple and can be served ...
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2answers
151 views

Redunt link over single cisco router

I have one cisco router 3825 with multiple WAN card connected to two ISPs and I have one 2811 with two WAN cards in branch offices. I need to configure these routers to connect both links and once one ...
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2answers
347 views

Two domain controllers - yet when primary is down, domain still fails?

I have multiple windows 2003 servers support a particular network, and when one particular server is taken offline, domain services begin to rapidly fail, such as users couldn't login. What check ...
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2answers
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One server, Two APC UPS on redundant power supplies : How to trigger shutdown?

I have a server racked and its redundant power supplies plugged in two APC Smart-UPS 3000 XLM. Each UPS is connected to two different mains power sources. Two instances of apcupsd are running, each ...
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4answers
347 views

System Monitoring Redundancy

I consult in a small business environment where I have two HyperV hosts (with <10 VMs) + a couple other servers. I recently had an issue where one of the HyperV hosts had a CPU issue and it came ...
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2answers
1k views

Can I get redundancy with a JBOD storage subsystem

I have a Promise Technology J610S. This is a JBOD subsystem. Is it possible for me to buy a SAS hardware RAID controller and provide some type of redundancy for these drives? I am unsure whether I ...
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1answer
185 views

Simple Central Storage for HA mail server

I will have 2 Postfix servers. One will be a backup of the other. What is the easiest method to provide central storage to both of these boxes? My infrastructure is very simple: Just a lot of Xen ...
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5answers
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Eliminate single point of failure for webservers?

I know in DNS, that each of the DNS servers will be tried to see if they will respond I know in email that in the event of a failure it will go to the next one in the list or it will hold the mail ...
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3answers
3k views

How to make two UPS redundant?

How to setup UPS for redundant power supply if 1st UPS goes down then system should work on 2nd UPS if 2nd goes down then system should work with 1st UPS like server power supply.
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3answers
439 views

Distributed redundant storage solution?

Is there a way to use extra space on computers as a distributed backup system? I'm thinking that using the extra space on the systems in my network would add a lot of storage to the available pool, ...
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4answers
486 views

Importance of Redundant Power Supply

How important are redundant power supplies in servers, not measured by how critical server uptime is, but by likelihood of failure? In other words, are server PSU's error prone and/or likely to fail ...
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1answer
182 views

Consistent Reliable Messaging

Hay All.. Im working a new project, Im currently deciding between flume & scribe for messaging systems... ( most probably sent to logs or hadoop ) I cannot lose a message ever.. What are ...
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2answers
616 views

redundant network handling in linux box

I need your help very badly. I have give a solution for the requirement. I'm struggling for 5 days to get one. Requirement is to get a solution for redundant network in Linux systems. We have ...
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1answer
337 views

distributed resilient storage system using existing linux spare disk space

tall order this request but I am hopeful... I have a bunch of servers (exactly 20) that each have about 2-7TB of free space, and that space is not in any danger of being used up soon. I was wondering ...
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2answers
55 views

mysql redundancy with mixed storage types

Looking at building redundancy into our system, as we are currently, um, exposed should anything blow up. We have a large-ish DB (150G), consisting of a mix of innoDB and myISAM table types. We want ...
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2answers
128 views

What to do if the failover fails?

I am looking to setup a failover in the following configuration - Failover Server (Frontend) Primary Server - Secondary Server (used if primary server fails) (Backend) So traffic goes to the ...
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3answers
444 views

How to make sure that in case of our mail server being unreachable (connection down) mail still gets queued and resent once it's back up?

We have had some issues with losing internet connection once in a while. Normally that would mean our mail server is unreachable and incoming email is bouncing. We've set up MX Backup (second MX ...
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1answer
328 views

Best way for Linux site and Database redundancy

I am looking to set up a redundant network that uses a load balancing solution to redirect traffic between two servers. The load balancer I will use is HaProxy. Example: Traffic -> Haproxy -> Server1 ...
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1answer
305 views

In equipment with dual PSUs, how is power draw balanced between them?

In equipment which has dual power supplies - e.g. a server - how is power draw balanced between them? Will they be "active/active", with load evenly spread between both PSUs? Or will they be ...
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3answers
532 views

Domain servers and redundancy

We have just setup our server (although I may be reinstalling it from scratch to use 2008 rather than 2003) and we are now looking into redundancy options. The best option I can see would be to have a ...
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5answers
193 views

Best way to add a second server to existing site in case of downtime?

Well my $379 dedicated sever just went cold again for the second time this month. I need to find a way to get another server going at a different provider that I can just flip on in case this happens ...