16
votes
Accepted
What's the difference between keepalived and corosync, others?
Here is the general rule of thumb I have used when deciding between keepalived and heartbeat.
Heartbeat is usually used when you want a true active/standby cluster setup (where only one node is ...
- 196
14
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 ...
- 7,756
14
votes
Accepted
Why Failover instead of Load Balancing for HA
The world is full of applications that were never designed with clustering in mind and terrible things happen when you try to run multiple instances of the application concurrently.
But the ...
- 74k
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 ...
- 9,536
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 ...
- 5,541
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 ...
- 115k
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 ...
- 196k
9
votes
Accepted
OpenVPN timeout to reconnect on fail takes a long time
The keepalive directive controls this:
# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# ...
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 ...
- 3,744
9
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 ...
- 630
9
votes
Accepted
Send PROXY protocol header from HAProxy
After posting on the HAProxy mailing list (haproxy@formilux.org) 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 ...
- 221
9
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. ...
- 4,494
8
votes
Is it not possible to use keepalived in EC2
Update 2021.
You can use it. But you probably shouldn't. There is very little justification to do so now. The Elastic Load Balancer should do most of what most people would need.
The accepted ...
- 14.3k
8
votes
Accepted
How to create a high-availability application server?
As your question is quite generic and doesn't give any details about the involved software, my answer is short as well: Just use a set of two loadbalancers, which share a 'virtual IP' between them via ...
- 5,541
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 ...
- 3,148
7
votes
Prevent HAProxy from toggling back from fallback to master
Use the stick 🏑 option. From the official HAproxy blog:
Automatic failover without failback
The configuration below makes HAProxy to use s1 when available, otherwise fail over to s2 if ...
- 3,220
7
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 ...
- 170
7
votes
How to create a high-availability application server?
Your load balancer should be made highly available, by the simple expedient of having two devices acting cooperatively. At any moment, one of the two devices is configured to have the load balancer ...
- 95.7k
7
votes
Accepted
How does High Availability work?
it works quite simple. First rule is you have to have anything more than once. For simplicity I will setup it in one datacenter and with IP addresses owned by this DC (you can do it with your own IP ...
- 2,633
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 ...
- 8,928
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://...
- 1,476
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 ...
- 937
6
votes
Accepted
What is the definition of High Availability?
My question was to determine if there is an precise definition of how much availability constitutes High Availability
There is no official definition of how much availability constitues "high ...
- 6,868
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 ...
- 5,286
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 ...
- 31.2k
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)...
- 6,151
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 ...
- 3,438
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-...
- 12.7k
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.
- 8,928
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 ...
- 8,928
Only top scored, non community-wiki answers of a minimum length are eligible