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16 votes

DNS Round Robin: Do browsers stick to one IP as long as it is online?

Each browser has it's own method of handling round-robin DNS, I've spent some time today researching this problem and will continue to update my answer as I find proof of implementation which will ...
Jacob Evans's user avatar
  • 8,046
12 votes

How to design/ensure high-availability of web servers?

High availability without some kind of load balancing using a dedicated server would not be possible. You would need to have 2 servers and there are some software options for load balancing. Windows ...
Anthony Fornito's user avatar
11 votes
Accepted

DNS issue with Failover IP from Hetzner

As promised, here goes my answer: Full disclosure: I'm not working for Hetzner, but worked for different companies in the past and present who used to colocate hardware at Hetzner. In case the ...
gxx's user avatar
  • 5,661
11 votes

Mathematically, how to calculate an uptime percentage based on a number of nodes and their respective uptime percentage?

Uptime is a slippery thing... If you want to calculate the availability of a service then it is simply amount of time service is available ----------------------------------- x 100 amount of time ...
user9517's user avatar
  • 116k
10 votes
Accepted

Keepalived send gratuitous ARP periodically

keepalived versions 1.2.20 and above support following config settings regarding gratuitous ARP, vrrp_garp_master_refresh is what I need. # delay for second set of gratuitous ARPs after ...
user373333's user avatar
10 votes
Accepted

Shared storage options for ESXi HA cluster

General notes (stream of consciousness): Think really hard about what you're trying to protect. Nobody uses VMware Fault-Tolerance. Okay, maybe someone does, but there are too many restrictions, and ...
ewwhite's user avatar
  • 198k
10 votes
Accepted

Send PROXY protocol header from HAProxy

After posting on the HAProxy mailing list ([email protected]) I got the answer that I need to add either send-proxy or send-proxy-v2 to my backend server definitions. My updated config file has ...
Wad's user avatar
  • 241
10 votes

RDS snapshot: how long does I/O suspension occur?

The answer comes from understanding how snapshotting works. At the start of a snapshot, a message (command) is sent to all applications to come to a consistent state and flush necessary data to disk. ...
John Hanley's user avatar
  • 4,954
9 votes

how to cache contents in HAProxy

don't use the wrong tool haproxy is a wonderful tool. It does not provide caching. A quick scan of the fine docs can verify this. Unless you want to patch haproxy you need to use a tool that does ...
chicks's user avatar
  • 3,829
8 votes

How to configure Failover IPs for High Availability with Hetzner Online

As this is an old answer I'm not sure if you are still looking for an answer. But I stumbled upon it looking for the best way on how to do this. The way Hetzner assigns a failover IP to a dedicated ...
Robbert's user avatar
  • 180
8 votes

DNS Round Robin: Do browsers stick to one IP as long as it is online?

All modern browsers implement this https://www.rfc-editor.org/rfc/rfc8305 Happy Eyeballs Version 2: Better Connectivity Using Concurrency Roughly that means that a server with fastest connection will ...
user602895's user avatar
8 votes

Mathematically, how to calculate an uptime percentage based on a number of nodes and their respective uptime percentage?

The chance of one server being offline is (1 - 0.95) The chance of both servers being offline is (1 - 0.95) * (1 - 0.95) = 0.0025 etc... So using your model and from a purely mathematical point of ...
Phil's user avatar
  • 3,178
7 votes
Accepted

Complete High Availability System

If you do have just one Synology box shared between your Hyper-V machines, it can still be considered as a SPoF. It dies, you lose all the LUNs sitting there. For true HA you would need a second NAS ...
batistuta09's user avatar
  • 9,151
7 votes

Creating a VSAN datastore

Move/reinstall ESXi to USB flash drives, one per each host. In that case, ESXi boots from the USB drive, so local storage is free to be used for VSAN. Use this guide to setup VMware VSAN https://...
A.Newgate's user avatar
  • 1,483
7 votes
Accepted

2 Different Public Address for High Availability

Yes, but how you implement this will affect the user experience when one of the systems fails. At it's simplest you can enter 2 address A records in your external facing DNS and users will be sent to ...
Doug's user avatar
  • 982
6 votes
Accepted

Clustering and/or Hyper-V replica?

I would recommend you to use your old hardware in another way. I would purchase a new Dell server with the similar specs and create a Highly Available cluster. You can take a look at StarWind Virtual ...
Stuka's user avatar
  • 5,865
6 votes

NAT gateway high availability - AWS

How many you need depends your RTO and RPO. Also, for reference, NAT instance and NAT Gateway (comparison). A NAT gateway is around $400/year depending on your region. It's highly available so you ...
Tim's user avatar
  • 33k
6 votes

"live" mirror of HA VM cluster?

1) Deploy a VMware vSphere cluster and use Fault Tolerance https://www.vmware.com/files/pdf/techpaper/VMware-vSphere6-FT-arch-perf.pdf feature on your virtual machines (as already mentioned above). 2)...
Net Runner's user avatar
  • 6,249
6 votes

How do multiple backup servers work in Nginx?

While it does not support multi-backup servers in a context as @Alberto Mendoza answered -- If you place the backups to another VPS running a NGINX load balancer to its own backups... this is a work ...
Devitgg's user avatar
  • 61
6 votes

How does Virtual IP work for failing over a TCP connection to a backup server to accomplish high-availability?

We should clarify some terms and technology. The image you show is that of a "Load Balancer." While technically, the Load Balancer will usually have one or more "frontend" IP addresses that connect ...
Appleoddity's user avatar
  • 3,870
6 votes

Site-aware cluster migrates VMs to random nodes, not to the preffered site

You need to ... (1) ... use something like Windows Server 2016 built-in Storage Replica (DR, so active-passive replication only). https://docs.microsoft.com/en-us/windows-server/storage/storage-...
BaronSamedi1958's user avatar
6 votes

Azure high availability solution with synchronization of website and SQL server data

You can configure StarWind VSAN on a top of just two virtual machines and get real highly-available storage solution in the cloud. I believe this manual should be useful for you, check it out.
batistuta09's user avatar
  • 9,151
6 votes

KVM+DRBD replicated between two active-passive servers with manual switching

Why not using things which have been checked by thousands of users and proved their reliability? You can just deploy free Hyper-V server with, for example, StarWind VSAN Free and get true HA without ...
batistuta09's user avatar
  • 9,151
6 votes
Accepted

High availability for ceph storage?

You need at least 3 MON to achieve HA because of the quorum. With only 2 nodes your storage will be stopped by an problem on one node. "When a Ceph Storage Cluster runs multiple Ceph Monitors for ...
batistuta09's user avatar
  • 9,151
6 votes

Am I doing this wrong? Networking - High Availability: SAN, MSFT Failover Cluster, NIC Teaming

(1) Storage. QNAP would make a decent backup target, say used over iSCSI with Veeam, but it's quite a poor choice in terms of the primary storage. Performance isn't great, but the worst part is... It'...
NISMO1968's user avatar
  • 1,060
5 votes

How to use Docker with HAProxy+Keepalived?

You may need to enable non-local binding on the docker host. Add net.ipv4.ip_nonlocal_bind=1 to the end of the /etc/sysctl.conf file and force a reload of the file with the sudo sysctl -p command.
Dave's user avatar
  • 151
5 votes

Hyper-v failover or replication in 2 node cluster

3rd party solution like StarWind virtual SAN. While this looks like it could work, they no longer offer the hyperconverged storage feature in the free version (ie can't be installed on a host running ...
BaronSamedi1958's user avatar
5 votes

keepalived - random re-elections

The problem is that you use the default state MASTER for the backup nodes. They should state BACKUP. vrrp_instance VIP_61 { interface bond0 virtual_router_id 61 state BACKUP ...
pj3s's user avatar
  • 51
5 votes

Mathematically, how to calculate an uptime percentage based on a number of nodes and their respective uptime percentage?

This depends on why your servers are down 5% of the time. If you have power 95% of the time, but your servers are otherwise flawless, then a second server at the same location does not increase your ...
Seamus's user avatar
  • 151
5 votes

Mathematically, how to calculate an uptime percentage based on a number of nodes and their respective uptime percentage?

First of all, the total availability or uptime of a cluster depends on how large a part of the cluster is needed to be active for the whole cluster to be considered 'up'. Is one functioning machine ...
ilkkachu's user avatar
  • 307

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