Questions tagged [redundancy]
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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Is Round-Robin DNS "good enough" for load balancing static content?
We have a set of shared, static content that we serve up between our websites at http://sstatic.net. Unfortunately, this content is not currently load balanced at all -- it's served from a single ...
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Probability of Blade Chassis Failure
In my organisation we are thinking about buying blade servers - instead of rack servers. Of course technology vendors also make them sound very nice. A concern, that I read very often in different ...
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How to make redundant load balancers?
I understand that the purpose of load balancers is to balance load between your servers and keep track of instance health, etc. But what if load balancer itself fails? How do you set up redundant load ...
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How to protect against loss of server on a budget
I'm a small company on not much budget providing websites and databases for charity and not-for-profit clients.
I have a few Debian Linux VPS servers and ensure I have daily backups to a different ...
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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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Is there any value in protecting both rack power feeds with their own UPS?
I've done some looking and have not found a satisfactory answer to this question.
When is it necessary or suggested to use an independent UPS (on it's own mains branch circuit) for each power feed to ...
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When is RAID worth the trouble?
In our shop we're faithfully using RAID in all our workstations, probably just because that seems to be the way it ought to be done. I'm talking about workstations for scientific simulations, using ...
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Is it possible to have a secondary managed DNS provider to quickly delegate to when DDOS attack on our *primary* external DNS provider happens?
So our DNS provider, every so often, experiences DDOS attacks on their systems that causes our front-facing web sites to go down.
What are some options in terms of reducing dependency on a SINGLE ...
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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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Correct way to set up DNS primary/secondary/... for redundancy and latency reduction?
I thought DNS primary/secondary for redundancy purposes was straightforward. My understanding is that you should have a primary and at least one secondary, and that you should set up your secondary in ...
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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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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 ...
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Can you set a backup IP for your server in DNS?
Is there a way that the DNS protocol can naturally hold a backup A record server address, like backup name server or mail server records? When searching for this I only saw results on backup ...
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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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VMware vSphere cluster design for site redundancy
I have a question about the best design for site redudancy when using vSphere clusters. A bit of background info about our situation first though.
We are a medium-sized company with two main offices,...
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Is Ceph possible to handle hardware RAID arrays (LUNs) as OSD drives?
I am pretty new to Ceph and try to find out if Ceph supports hardware level raid HBAs.
Sadly could not find any information. What I found is, that it is recommended to use plain disks for OSD. But ...
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Redundant Power Supply Sloshing (If sloshing is the right word)
I have a Supermicro Redundant Power Supply with two units in it. I also have two UPS units, one for each of the Power Supplys. I was watching the LCD on the UPSs for the watt usage. The total watts ...
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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 ...
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Increase reliability by partitioning disks of different size?
I understand ZFS would prefer all disks carrying the same size. However, in the case that I have two disks with different size (1TB and 1.5TB), I'd like to have certain redundancy, but not mirroring. ...
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A-Record Failover?
I have a Fortigate 100D with 2x BT Business Infinity Fibre connections acting as WAN1 & WAN2.
The BT lines come with 5 static public IPs each and I have my DNS hosted through CloudFlare pointing ...
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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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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 ...
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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 ...
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If a RAID controller fails, does it disrupt service until it's replaced?
If I have 2 drives in a RAID 1, and the Raid Controller fails, does that mean the websites on the server will have downtime until the controller is replaced? Or does everything still carry on as ...
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Linux console is unusable when LDAP server is down
When our OpenLDAP server lost power the CentOS machines' console became nearly unusable.
We were trying to login with a local account, but each command would take minutes to return. Even simple ...
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How to setup redundancy for AWS Elastic Load Balancers?
In the spirit of redundancy and fail-over, I would like to know some strategies on setting up AWS Elastic Load Balancers for DR, that is, if this is really an issue? (A single ELB would LB traffic to ...
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How do I configure NAT rules when using ASA IP-SLA when leveraging post-ASA-8.3 NAT syntax?
We are currently running ASA9 at a location with redundant ip connectivity. We'd love to configure ip sla so that internet access survives a single carrier outage. I'm aware of the ip sla commands, ...
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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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Getting Started with NIC and Switch Redundancy
Currently with my servers, they all or almost all have 2 nics with one in use. Each NIC is is of course connected to a single switch.
What do I need to do to make this redundant in that both NICs ...
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SQL Server clustering options
Can anyone give an high-level overview of the options available for SQL Server clustering, their pros and cons?
Is it better to use Microsoft Clustering services or SQL Server native clustering? Does ...
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How far should we take the N+N redundancy craziness?
The industry standard when it comes from redundancy is quite high, to say the least. To illustrate my point, here is my current setup (I'm running a financial service).
Each server has a RAID array ...
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NTP: How to establish redundant solution for NTP servers?
In my company's infrastructure there are 5 data centers in remote locations.
In each remote location, there's a pair of servers which hold DNS and NTP services and are configured on each one of the ...
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Plug single PSU into two different power sources
We have a rather uncommon situation:
We have a server in a computer center. Its got not enough spare space to put in a redundant PSU. Nevertheless, we want to attach the single PSU to both existing ...
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ZFS RAID0 pool without redundancy
I created a ZFS pool on Ubuntu 14.04 without specifiying RAID or redundancy options, wrote some data to it, rebooted the machine and the pool is no longer available (UNAVAIL). I don't have the exact ...
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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 ...
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Self-healing archive file format with redundancy
When I used RAR, I had an option to add some extra recovery data in order to be able to cope with a not-perfect medium (think floppy disks). It saved my day several times, specially when dealing with ...
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How should the EFI System partition be made redundant without using hardware RAID?
What is BCP for making the EFI System partition redundant without using hardware RAID?
If I create 3x EFI System partitions on different devices and then backup any changes made to the primary (...
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How to setup redundant ejabberd servers?
I currently have an ejabberd server running at domain A. It has a bunch of users with accounts like xyz@A. I want to setup alternative servers so that if A is down, clients can transparently use ...
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Redundant links from Router to Switches
With a setup of two NICs on a server into two different switches where each NIC has a different IP (But both on the same network), and then the switches to the router. How would I configure the two ...
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Evaluating uncorrectable ECC errors and fallback methods
I run a server which has just experienced an error I've not encountered before. It emitted a few beeps, rebooted, and got stuck at the startup screen (the part where the bios shows its logo and begins ...
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Which is more standard in large enterprises: RAID5 or RAID10?
Which is more standard in large enterprises: RAID5 or RAID10?
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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.
...
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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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Should redundant servers have exactly the same configuration, or slightly different?
If you provide a service on two servers to ensure high-availability, is it better to configure them in exactly the same way, of instead should you introduce slight differences to prevent "freak ...
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Redundant NFS on Amazon EC2
I'm interested in building two fault tolerant/redundant NFS servers with failover at Amazon EC2. I'm familiar with tools/technologies like DRBD, Heartbeat, etc. Does Amazon provide any specific way of ...
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What hardware & software consideration does a major website require to properly manage 1000+ servers? [closed]
Sorry for such a high level question. I understand the basics of server load balancing, but the concept of managing 30,000 servers is a bit foreign to me. Is it really just the same concept of ...
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Redundant Linux Servers in Seperate Datacenters
I have 2 CentOS linux servers in separate data centers on each site of the country. These linux machines run a small web sites on Apache with a MySQL backend. There currently is no VPN connectivity ...
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redundant nfs share
We are storing files on a network share, our application is mountig this drive using nfs. Now we have the requirement to have this drive redundant.
We can add a second server and then synchronize ...
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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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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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