What is Data Persistence?

03 Feb 2023

What is data persistence, and why is it so important? Data persistence is a concept by which you can define the piece of information that will be stored on the device. Data persistence consists of all saved data in the storage system, which allows you to restore the value of this data at any time. You'll be able to restore all-important programs and info, even after a computer crash. Understanding the importance of persistence is essential to evaluate different storage systems accurately. You can lose your data by making the wrong choice. That is why it is worth considering the Drupal database migration. Any time a created process needs persistence, it's worth using non-volatile memory instead of volatile memory.

What Is Persistent Data?

Persistence means the process where the code that created the files stops working, but all those files still exist. Data can be allocated in structured, unstructured, and semistructured forms. A data store will be considered persistent if it writes to non-volatile storage every time. Developers should also consider data persistence. By connecting the saving of all important information, you can automate your business, and you will not lose any information.

Two types of the persistence

There are two types of permanence: the permanence of processes and the permanence of objects.
1. The permanence of processes
The first type is all processes that aren't closed until the user needs them. The main processes of a computer system can be classified as permanent since they ensure the good operation of the device. 
2. The permanence of objects
The second type refers to an object that persists until you delete it from the computer's memory.

Data can be considered persistent because the software is constantly updated, and all information remains the same. They are often hosted on servers and used more frequently than archived data. All your data in the form of objects and records are stored in a permanent database. They will be saved even if you change devices and software. Persistent data can be restored because it is stable. You can recover important data even after a complete system restore. They are stored as records and tables in traditional relational database management systems (RDBMS). 

Data persistence: Example

A simple example of data persistence is loading and saving files within an application. For example, a previously created and saved file is opened while listening to music or viewing photos. Occasionally, technical problems can cause the browser to close the page. After restarting the browser, you are prompted to resume all tabs. The ongoing data process is your insurance in case something goes wrong.
Another example of data persistence is the personal information on your Facebook page. Each time you fill out a registration form, your data is stored in a persistent database. When you visit the site again, you'll see persistent data. All core operating system processes remain persistent to keep your device or workspace data in its original state each time you turn on the system.

What is persistent storage?

Persistent storage can be any device that hosts and stores user data. The second name for persistent storage is non-volatile memory. It is usually related to applications that can be tracked. For example, databases remain available even after containers shut down. Persistent storage volumes are vastly superior to ephemeral ones that stop working when the application closes. Persistent storage is used for all the necessary data that the user needs.

Generally, there are two types of storage:
1. Containers. They are available on the OpenStack platform. It can be used to store various objects and statistical data. All objects are organized using containers. All data can be viewed through the REST API since the volume's contents are only accessible through instances. Therefore, every service uses object storage.
2. Kubernetes. OpenShift uses them to organize all applications on a cluster. It is no longer necessary to provision and registers storage volumes before use. This allows you to specify the user who created the volumes for the application.

In-memory  Database vs Persistent Database


An in-memory database system (IMDS) allows you to store all the necessary data in RAM. Unlike common databases that store information on permanent media, IMDS manages application data much faster. Operational databases are simpler in design than persistent databases and therefore take up less memory. Accordingly, working with data takes less time than reading and writing the entire file system, which makes it faster. The team that developed this system decided to focus on performance and ease of use of storage space. IMDS may not use a cache and therefore does not need the LRU algorithm that would typically maintain cache contents.

Persistent Database

A persistent database stores information on a hard drive or solid-state drive. It is specially optimized to reduce input and output processes. The database system uses disk space and device memory to accomplish this. In turn, the cache keeps extra copies of the persistent database in memory. CPU cycles determine what should be in the cache. This allows you to find any necessary information quickly. There is also an index system. An extra copy of the data is stored in the index, so the user does not have to insert and eject the disk constantly. The additional CPU cycles and memory greatly simplify the operation of persistent database systems.

Why is persistent data important?

  • Permanent data don't change over time; therefore, it is considered statistical.
    All important information is in permanent data. They are stable because objects and processes are preserved until the user himself decides to delete everything. 
  • Permanent data is independent of time.
    If the information was created, it would remain on the device after deletion. All major system processes reside in non-volatile memory, which makes it possible to achieve process persistence. Persistence allows you to save important information to an external file. The user can use a special code to further access the data in this file. Due to persistence, this code does not reset after each application.
  • Data remains in its original format at all times.
    They are removed from volatile
    memory only after the process is completely closed. All information is non-volatile, which makes it possible to withstand power outages. You can restore all programs even after a complete shutdown of the computer. All necessary permanent data will be available to you at any time.

 How to add persistence to your systems?

A common method of adding persistence to a system is periodically writing all the data to disk, setting the desired interval. All updates released during this period will be lost. The durability of all the information on your device can only be ensured by persistence based on the commit log. You can run updates on a pre-installed record, ensuring the entire process's performance and security.

Which data stores provide persistence?

Users must understand how the four main design approaches affect persistence to achieve persistence.
1. Pure in-memory – there is no constancy at all.
2. In-memory – has snapshots.
3. Disk-based – the update is written immediately.
4. Commitlog-based – works like well-known OLTP databases.
In-memory has limits on the amount of data, which ensures good speed. All workloads share a small amount of data in common. Special systems are being created that allow you to place the entire data set in the device's memory. After the process is completed, the data will be completely deleted. This means that the types of data stores listed are not persistent.
Tapes, disks, and other magnetic and optical media are persistent types of storage. There are files, objects, and block storage types. Persistence is one of the main requirements of various storage systems, whether a cloud service or a network system.

To sum up

The concept of database persistence refers to how processes or objects can continue to run and remain even after the system is shut down. Earlier, we explained what persistence in databases is and what types of persistence there are. Moreover, now you know how vital persistent data is. We hope you enjoy this type of blogging as well. We are happy to be of service to you. It's your Golems team!