Sql Server Log Shipping Vs Replication – Using a PostgreSQL database copy can be useful not only for high availability and fault tolerance, but also for improving the performance of your system by balancing traffic between standby nodes. In the first part of this two-part blog, we will see some ideas regarding PostgreSQL replication.
There are different methods for copying data in PostgreSQL, but here we will focus on two main methods: streaming data copy and logical copy.
Sql Server Log Shipping Vs Replication
PostgreSQL streaming replication The most common PostgreSQL replication is a physical copy that replicates changes at the byte level, creating an exact copy of the database on another server. It is based on the log shipping method. WAL records are passed directly from one database server to another for implementation. We can say that this is a kind of continuous PIT.
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This WAL transfer is done in two different ways: by transferring one WAL record file (WAL segment) at a time (file-based log delivery) and by transferring WAL records (WAL files consist of WAL records). ) between the primary server and one or more waiting servers without waiting for the WAL file to complete.
In practice, a process called a WAL listener running on a standby server will connect to the server using a TCP/IP connection. On the other server, it is called the WAL sender and is responsible for sending the WAL registry to the waiting server when it happens.
When setting up streaming, you have the option to enable WAL persistence. This is optional, but very important for installing a solid state copy, as it is necessary to avoid the server processing old WAL files that have not yet been applied to the standby server. If this happens, you will need to recreate a copy from scratch.
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PostgreSQL logical replication is a method of copying data objects and transforming them based on their replication IDs (usually a primary key). It is based on a publish and subscribe mode in which you subscribe to one or more publications on one or more publisher nodes.
A print is a change set created from a table or group of tables. The node where printing is defined is called the publisher. Subscriptions are the basis of logical replication. A node for which a subscription is defined is called a subscriber, and it defines a connection to another database and a set of publications (one or more) to which it wants to subscribe. Subscribers download data from the publications they subscribe to.
Logical replication is built on an architecture similar to real streaming replication. This is done by the Walsender and Applied processes. The walsender process initiates WAL logical decoding and loads the standard logical decoding plugin. The plugin converts read readings from WAL to logical copy protocol and filters the data according to the publication specification. The data is then transferred using a streaming copy protocol to an executor, which maps the data to the underlying table and makes individual changes as they come in in the correct working order.
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A logical copy starts by copying the data from the publisher’s database and copying it to the subscriber. The original data in the existing subscription table is preserved and copied to a parallel instance of the implementation process of a specific type. This process will create its own temporary copy hole and copy existing data. After backing up existing data, the employee goes into sync mode, which ensures that the table is brought into a state that is in sync with the main implementation process of any flow of changes that occurred during the backup. Raw data using standard logical replication. After synchronization is complete, control of the table copy returns to the main implementation process, where copying resumes normally. Changes to publishers are sent to subscribers when they happen in real time.
This is the default mode. There may be some operations running on the primary that have not yet been copied to the standby. This means that there is a possibility of possible data loss. This execution delay is very small if the waiting server has enough capacity to hold the load. If the risk of losing this small amount of data is unacceptable within a company, a synchronized backup can be used instead.
Committing each write operation will wait for confirmation that the commit has been written to a pre-written log on the disk of the server and the waiting server. This approach reduces the chance of data loss. For data loss to occur, you will need to initialize and wait for a failure at the same time.
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The disadvantage of this method is the same for all synchronization methods, since this method increases the response time for each write operation. This is due to the need to wait for all confirmations that the transaction has been completed. Fortunately, this issue will not affect read-only operations; Write operations only.
High availability is a requirement for many systems, no matter what technology we use, and there are different ways to achieve this with different tools.
Load balancers are tools that you can use to manage the traffic of your applications in order to get the most out of your database architecture. Not only is this useful for load balancing our database, but it also allows us to redirect applications to existing/healthy hosts and even specify ports with different roles.
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HAProxy is a balancing device that distributes traffic from one source to one or more destinations and can define specific rules and/or protocols for this task. If any destination stops responding, it is marked as free from the Internet and traffic is routed to the remaining destination. Having one Load Balancer node will create a single point of failure, so to avoid this you should deploy at least two HAProxy nodes and configure Keepalived between them.
Keepalived is a service that allows us to set up virtual IP addresses in active/passive server groups. This virtual IP is assigned to the active server. In the event of a failure of this server, the IP is automatically transferred to the “secondary” passive server, allowing it to continue operating with the same IP in a manner transparent to the system.
Performance is always important in any system. You will need to make efficient use of available resources in order to provide the best response time possible, and there are different ways to do this. Each database connection consumes resources, so one way to improve PostgreSQL database performance is to establish a good connection between your application and the database server.
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Connection integration is a method of creating a set of connections and reusing them to avoid constantly opening new database connections, which will greatly improve the performance of your application. PgBouncer is a popular connector designed for PostgreSQL.
PgBouncer acts as a PostgreSQL server, so you just need to access your database using PgBouncer information (IP address/hostname and port) and PgBouncer will connect to the PostgreSQL server or be reused if it exists.
Once connected, PgBouncer performs validation based on the method specified in the configuration file. PgBouncer supports all authentication mechanisms supported by PostgreSQL servers. After that, PgBouncer checks the cache connection with the same username + built-in database. If a cache connection is found, it returns the connection to the client, otherwise creates a new connection. Depending on the configuration of PgBouncer and the number of active connections, new connections may be queued until they can be created or even deleted.
Extend Sql Server Dr Using Log Shipping For Sql Server Fci With Amazon Fsx For Windows Configuration
With all these concepts outlined in the second part of this blog, we will see how you can combine them to create a great PostgreSQL architecture replication environment.Ar Cloud Operations and Migration for Gaming Marketplace News Affiliate Network Smart Business Big Data Business Productivity Cloud Enterprise Strategy Cloud Financial Management Computing Contact Center Containers Database Desktop and Application Streaming Developer Tools DevOps Front-End Web & Mobile HPC
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