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15 votes

PostgreSQL High Availability/Scalability using HAProxy and PGBouncer

Your existing configuration of HAProxy -> PGBouncer -> PGServer approch is better. And that only works. Here is the reason: HAProxy redirects connection to different servers. this results in MAC ...
Jobin Augustine's user avatar
11 votes

By Mistake Deleted AlwaysOn Availability Database from live Production Server

It is not possible to delete a database that currently resides in an availability group. It is also not possible to restore over top of it while it remains in the availability group. Thus, this ...
10 votes
Accepted

Always On FCI vs Always On Availability Groups

What is the advantage of Always On Failover Clustering vs Always On Availability Groups? The main advantages given 2012->2017 for an FCI is: No instance level metadata or objects required to be ...
Gavin Belson's user avatar
10 votes

What is the best option for High availability on a data warehouse?

Most data warehouses are in Simple recovery model, and most true HA solutions require Full recovery (AGs, Mirroring). The minimum for Log Shipping is Bulk Logged, but that's not really true HA since ...
Erik Darling's user avatar
  • 41.9k
10 votes
Accepted

Avoid downtime of Microsoft SQL Server during restarts

If you have a running query or an open transaction, SQL Server doesn't have a way to move that query or transaction over to another server. When your SQL Server instance (we'll call Instance A) ...
Brent Ozar's user avatar
10 votes
Accepted

Availability Group - how much data was lost after forced failover

Go to SSMS Object Explorer Expand Always On High Availability Expand Availability Groups Right click your AG Select Show Dashboard In the dashboard, above the list of AG databases and their status, ...
Aleksey Vitsko's user avatar
8 votes

High Availability SQL Server

A solution that will work with SQL Express would be ideal, SQL Standard is fine, but I dont want to have to upgrade to SQL Enterprise. If you want something straight out of the box, that's going ...
Sean Gallardy's user avatar
8 votes
Accepted

Does a replica set with only two machines make sense?

If a primary member unexpectedly dies, the secondary one won't elect itself the new primary anyway, since it won't have the majority (which is two in a replica set of two machines). This is correct. ...
Stennie's user avatar
  • 10.3k
8 votes
Accepted

Always On Primary Replica On Prem, Secondary Replica On Azure

We only want to have 2 replicas, one on-prem and one on azure. Is this possible? Yes, it's possible. There are extra items you'll want to think about such as having a domain controller (if ad-...
Sean Gallardy's user avatar
7 votes

Restart the active node services without failover

Use the Failover Cluster Manager application to manually stop the services. This tells the cluster you are intentionally shutting down the service, so it won't attempt to bring it back up on another ...
Hannah Vernon's user avatar
  • 70.2k
7 votes
Accepted

What reason could cause AWS RDS connections to spike

If you run show processlist; it'll show you all the connections that are running against your DB. Running show status like 'Conn%' can show how many connections are active You may think that a high ...
Ste Bov's user avatar
  • 2,081
7 votes
Accepted

Adding indexes to production MySQL database without downtime?

If you wanted to add indexes to a live table, there are two major approaches: APPROACH #1 : pt-online-schema-change (Preferred Choice) This tool is spectacular. It will create a temp table for you and ...
RolandoMySQLDBA's user avatar
7 votes
Accepted

SQL Server AlwaysOn Availablity Group Automatic seeding

You should be able to see the reason automatic seeding didn't complete by looking in the SQL Server error log from the time period where you created the AG (on both the primary and secondary replicas)....
Josh Darnell's user avatar
  • 29.4k
7 votes
Accepted

Why putting SQL Agent offline caused WSFC to fail over on passive node?

If you look in Failover Cluster Manager, if you select the role for the Failover Cluster Instance (FCI) Role, then select the "Resources" tab at the bottom you'll see that the role is ...
AMtwo's user avatar
  • 16.2k
7 votes

SQL Server Connection String - MultiSubnetFailover True or Yes?

Are both "Yes" and "True" supported? Or does it vary by driver? If the latter, is there a list of which drivers support which syntax? Every driver has their syntax. In the first ...
Sean Gallardy's user avatar
6 votes
Accepted

SQL Server Always On or Mirroring & Log Shipping

If you were referring to Database Mirroring when you say mirroring (as opposed to SAN mirroring), then don't. It has been deprecated since 2012 now so it is a potential candidate for complete removal ...
SQLmojoe's user avatar
  • 1,433
6 votes

Automatic failover support on SQL Server having only two servers

For automatic failover, you need a tie-breaker. Otherwise, what would happen when the two servers had a network split and couldn't see each other? You wouldn't want them both automatically promoting ...
Brent Ozar's user avatar
6 votes

AlwaysOn AG versus FCI

In general, FCI is more beneficial compared to AG because of various reasons already mentioned above. Of course, 2-node FCI is completely great but should not be built on top of storage spaces direct ...
Net Runner's user avatar
6 votes

What reason could cause AWS RDS connections to spike

In your RDS, first check all IOPS metrics. RDS provide a certain quantity of IOPS, and if your RDS Instance have 10GB SSD, probably your IOPS quantity is 100 IOPS (default), this value increase ...
Gustavo alves's user avatar
6 votes
Accepted

Estimated recovery time and REDO queue size related to DB up time

Estimated Recovery Time is how long SQL Server thinks it will take to run the recovery process required to bring the database into read-write, usable state. 4600 seconds is a LONG TIME. You should ...
Hannah Vernon's user avatar
  • 70.2k
5 votes
Accepted

Mongo CP, Cassandra AP?

C stands for eventual consistent. Correct ? Consistency in the CAP theorem is referring to strong consistency where every read receives the most recent write or an error. By default MongoDB drivers ...
Stennie's user avatar
  • 10.3k
5 votes
Accepted

MongoDB stepDown fails in a PSA Architecture

There is No electable secondaries because priority of secondary node is set to 0 (see rs.conf() in the original post. Thanks to Mani for his suggestion!). I updated priority (and votes) for lxc-...
Nicolas Payart's user avatar
5 votes
Accepted

HADR_SYNC_COMMIT waits on SQL Server

I wanted to say kudos for diving in and investigating using XE, that's definitely a correct step in the eventual solution. Having said that, it's unlikely we're going to be able to directly help in ...
Sean Gallardy's user avatar
5 votes
Accepted

Can I use different endpoint URLs for the primary replica in a SQL Server Availability Group?

Is it possible to explicitly use different endpoint URLs for the primary replica for different replicas in an SQL Server Availability Group? No, it is not. There can only be one database mirroring ...
Sean Gallardy's user avatar
4 votes

Postgres database zero down time production deployment

Answer originally left as a question comment. For zero downtime during tables refactoring, we create new tables along with old ones, and switch in small steps. From Developing Low-Maintenance ...
4 votes

PostgreSQL High Availability/Scalability using HAProxy and PGBouncer

I have to disagree with the answer provided by donatello. You see, if your application doesn't manage DB connections using a local pool, it will create a new connection each time it needs to query ...
Alvaro's user avatar
  • 41
4 votes

SQL Server Database Mirroring is going to die. How can I guarantee high availability now?

Basic Availability Groups available in Standard Editions of SQL Servers 2016 forms a like to like replacement of Database Mirroring and has exact similar features. Both available for Standard ...
Masood Hashim's user avatar
4 votes

SQL Server Always On or Mirroring & Log Shipping

I would recommend you to use Always on availability group for server reasons. Database mirroring is deprecated as of SQL Server 2012 and will be removed on the future versions, so it is better to ...
Hailegziabher Dechassa's user avatar
4 votes
Accepted

SQL Server 2014 - AlwaysOn HA - Always Synchronizing

Since you have configured AlwaysON as Asynchronous, it will be in synchronizing state. Should it say Synchronized at some point? If you want to do a planned failover, you should alter your ...
Kin Shah's user avatar
  • 62.3k
4 votes

Automatic Failover or Database Mirroring?

What you're describing sounds like Microsoft Sql Server HADR commonly called AlwaysOn Availability Groups. It combines traditional Windows clustering with Database Mirroring to allow you a primary ...
Richard L. Dawson's user avatar

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