There has been a lot of talk and writing about backup lately. And we, SIM-Networks, including. :)

The fashion theme is inevitably mythologized. We tend to fill in the gaps in our knowledge with fictional facts and subjective assessments. This happens, in particular, with regard to the service Reserve copy and the question of its organization by hosting providers. Should a hoster provide its clients with backups automatically, by default? The answer to this question can be found in our material

The increased interest in the topic of backups is not surprising: given the active development of malware, antivirus outpacing the development, it is most rational to build IT security around the system backup save information - instead of wasting resources on preventing attacks and fighting viruses, it is much easier, cheaper and easier to restore the system and saved data from up-to-date backups.

In addition, an up-to-date backup will help mitigate the consequences of force majeure or human factors, as well as equipment failure due to various reasons. No wonder, after all, one of the commandments of the system administrator says: cooking new server to work, first set up a backup!

How to set up a backup

You can make a backup yourself - there are enough tools today, Google will be happy to tell you. But if you are not a cool pro in the field system administration, it is better to trust those who are competent and able to set up a backup, fully responsible for the result.

It is very important to pay attention to two points: copies of information that is critical for you should be made regularly, and stored in a remote place, as far as possible from the originals.

The first point is important because the information at the time of recovery should be as relevant as possible for you. For example, if your system is infected with a virus and the only way to get back valuable data is to restore it from a backup, then, you see, it will be very disappointing if the most recent copy of your financial statements is dated last month.

The importance of the second point can be illustrated as follows: if your backup storage for backups is located on the same server as the main system, then if the server burns down, everything will really burn down. Final and irrevocable.

Therefore, we take care of the correct backup schedule and ensure the remote storage for copies.

The main criteria for choosing a program for backups

In the event that you still want to take the risk and organize the backup of your data yourself, experts recommend four universal criteria when looking for a backup program:

• resource efficiency: the program should work in the most autonomous mode (without distracting you and not wasting your time resource, that is, automated as much as possible), with the minimum possible load on system resources and run in the minimum possible time;
• recovery speed: The software should restore your data from a backup as quickly as possible so that business processes do not suffer; the ideal would be the function of working directly with copies of the data;
• data protection and security: a backup program must necessarily provide you with an adequate level of security - both cryptographic and hardware (protection of data transmission channels in the storage system, data protection during a backup operation, the ability to restore an interrupted session);
• flexibility: The software should be equally suitable for all types of data (since it is impossible to predict which ones you consider critical and choose to copy to backup storage), and also give you the opportunity to choose backup methods and function equally well with any of them.

Modern software used by professional admins always meets these criteria. In addition, people who are specially trained and have rich and varied experience in setting up backups can choose the most optimal backup option for each specific case. Therefore, we still strongly recommend that you seek help from specialists so that later it will not be excruciatingly painful from the erased correct copies, over which erroneous information is written. It is clear that restoring such backup versions will not bring you the desired result, because the original correct data is lost. This happens if an inappropriate copy method is selected and the amount of backup storage is too small.

Now let's talk about the types of backup - full, incremental and differential. They differ in the way information is copied and compressed.

Full backup (full backup)

Everything is clear from the name: each time, according to the backup task, a complete copy of the entire system is created, more precisely, all the data that you specified for backup when setting the task. To reduce the total backup volume, all data is compressed into an archive. Thus, in your storage, with a full backup at a given frequency, archives appear where the data is mostly duplicated (because it has not changed for a long time). This is a serious disadvantage, because a huge amount of resources is consumed (see item 1 in the list of backup criteria): storage space, creation time and processor time, computing power, finally, traffic resources when transporting archives to a remote storage system. And although the full copying method was previously very common due to its high reliability, today it is recognized as ineffective in its pure form. For example, for backups of low depth (less than two weeks) or high frequency (once a day, once every few hours) full backup overuses resources.

The mechanism will save the situation a little deduplication- identification and removal of duplicate data in full copies. It is also given by special software tools both at the storage or server level, and on the client directly. Statistics in some sources give impressive results of the degree of deduplication - from 90% to 98%.

The advantage of a full backup can only be called the speed of recovery: when data is raised from one archive, it happens faster than with an incremental or differentiated backup.

Today, the full backup method is usually used exclusively as a basic one in combination with other less resource-intensive methods. Sometimes this approach is also called mixed or synthetic backup.

Incremental, or incremental, backup (incremental backup)

Compared to a full backup, it is much more economical and faster, since this process copies only those files that have changed since the previous backup. The original data originally recorded is not overwritten. The mechanism of incremental copying is simple: the time (for example, midnight from Sunday to Monday) at which a full backup is made is selected as the starting point for X 0 backup; at point X 1 (midnight from Monday to Tuesday) files that have changed and/or appeared since X 0 are copied; at point X 2 (midnight from Tuesday to Wednesday) the files that have changed/appeared since the execution of X 1 are copied; ... at point X n the cycle ends and the next full backup is made.

This method is much more economical in terms of resources and storage space, and time and data traffic, compared to others. However, when restoring data, if necessary, from a backup, a phased restoration occurs from points X n-1 ... X 2, X 1, X 0 - up to and including the last full backup, and this process can take a long time.

Differential backup

Wins over incremental in case of data recovery - it has less time for this operation, since full copies of X 0 and X n are compared and no phased recovery is required. However, in terms of storage space, differential backup is comparable to full backup, so saving storage space and traffic is practically not achieved.

With a differential backup, a “cumulative total” is copied: each changed file at each subsequent backup point is copied anew. That is, it looks like: X 0, X 1, X 1 + X 2, X 1 + X 2 + X 3, ... + X n, X 0 + X (1 + ... n)

In a word, it is very cumbersome and difficult when calculating storage space.

Understanding the difference between incremental and differential backups is quite simple. In fact, it is in one word. Just compare:

• incremental processes files that have been changed or created since the previous backup;
• differential processes files modified or created since the execution of the previous complete backup.

Other types of backup

A type of differential backup is delta copy (delta block or delta style backup). With this method, only the changes that occur in the files are written to the copy, and the completely changed data is not overwritten. That is, a part is copied, not the entire file. True, the delta-block method can be applied specifically to files being modified, and not to created files - therefore, new files are copied in their entirety.

It distinguishes high speed creation, extreme space savings and significantly less (in comparison with incremental and differential backups) the amount of redundant data. It would seem that everyone should use the delta, but this does not happen, since backups are created in this way and information is restored using special software. In addition, restoring from a delta backup takes a very long time: data has to be collected from a mosaic of changed pieces. However, this method is convenient to use to ensure continuous data protection (when a file is backed up immediately after it is created or changed - a mechanism that vaguely resembles autosave in Word's files))) or in cases of reduced throughput when saving backups on remote storage.

Similar to the delta block backup, the developed by programmers binary patch method, in which parts of the changed files are copied, but a different comparison base is used (in the delta - blocks, in this method - bits of information).

However, keep in mind that both methods mentioned are used in conjunction with differential or incremental backups, but not on their own.

Sometimes referred to as backup technology mirroring, used, for example, at the hardware level in RAID1 or when creating mirror sites. In essence, this is a simple copying of original and modified files, without archiving and systematizing the accumulation of modified files in a given period.

Over the past 12-15 years, there have been many critical changes in backup technologies that have forced us to reconsider the effectiveness of approaches and discover new ways. For example, the introduction of technology snapshots (snapshots) - snapshots file system, from which you can "glue" a backup copy - allow you to cloud systems make backups quickly and painlessly without stopping virtual machine. In addition, when used in the cloud, snapshots can seriously save storage resources, since they do not take up space on the client's disk.

SIM-Networks customers choose backup!

Of course, if you like to do everything yourself, it will not be a problem for you to set up manual backups - on your home computer. True, even in this case there is a partial risk, because something can go wrong, and valuable photographs, books, videos or rocket stage calculations may accidentally not be saved or be saved with a defect that makes it impossible to restore them from a backup copy. What about office machines? What if it is necessary to provide a backup of the data stored by the corporate infrastructure? We recommend that you still rely not on your own strength, but on the professionalism of the hosting provider. Ordering a backup setup and offsite backup storage space in Germany is very easy.

Backing up business-critical data has become essential these days. It is also part of the comprehensive measures to ensure information security companies we wrote about in the material

If you rent capacity in our cloud infrastructure, ordering the SIM-Cloud BaaS backup service is as easy as shelling pears, in a couple of clicks. Everything is already set up and will be connected automatically as soon as you give the command. By the way, when our engineers were developing SIM-Cloud BaaS, they analyzed the efficiency different types backup and opted for the incremental copy method. Our cloud backup is optimized so that the RTO (time to restore data from a copy) averages from 15 to 30 minutes, depending on the amount of data. Cloud BaaS from SIM-Networks meets all the above criteria for high-quality backup.

You can independently choose in which data center to organize storage for backups. The first option is local storage: your backups are stored in the same DC where your main infrastructure is deployed. This makes it possible to speed up RTO and RPO. The second option - backups are sent for storage to a data center remote from the one in which the main infrastructure is deployed. Data recovery in this case will be a little slower, but the security factor is higher. If you're not sure which option to choose, contact our Customer Care team to help you find the best solution.

And for adherents of the classic hardware, we offer rental for backup copies: reliable, safe, high-tech. And, of course, our highly trained support experts will help you configure the required frequency, depth and other backup options for your system.

Backing up your data is something everyone should do regularly. active user a computer that does not want to lose all of its information (or some of it) in the event of an unexpected failure. Often in various applications, designed to back up information, you can find three mechanisms for how to create a copy: completely, incrementally or differentially. In the framework of this article, we will consider how these copying methods differ from each other.

Table of contents:

Data backup methods

There are many programs that are designed to create a backup copy of information, both in the Windows operating system and in Mac OS. All of them perform approximately the same actions - create a backup operating system, completely copy the disk, some of its partitions, folders or other data, depending on the settings selected by the user. After that, these backups can be used to restore information.

The created backup copy needs constant updating. Based on the backup creation conditions applied in the program, you can create a copy, while choosing a backup mechanism:

• Creation of a complete copy;
• Generation of an incremental copy;
• Creation differential copy.

These actions are available in many applications, for example, in one of the most popular programs for data backup, AOMEI Backupper. Within the framework of this article, examples will be considered on it, but you can find similar backup mechanisms in other programs.

Full backup

With this backup method, system snapshots that are generated within the same backup task can work independently of each other. Damage to one of these snapshots will not affect the operation of others. That is, with a full backup, a snapshot of the system contains all the backed up information.

The full backup method is the most reliable, but also the most wasteful in terms of resources. To back up the operating Windows systems and a few small applications, tens of gigabytes are required. Accordingly, constantly saving such full-fledged backups and storing them on the hard drive is irrational and wasteful in terms of free space on the drive. That is why the other two mechanisms discussed below are used.

Incremental backup

Incremental data backup implies that when creating a backup, the user once generates a full copy of the system and all files, and all copies created in the future are children of the main and previous ones, that is, they contain only information about the changes that have occurred - deleted, modified and created files.

Thus, each subsequent incremental copy after the first contains only information about changes. It looks something like this:

• Second copy. Child - contains information about data changes since the creation of the first copy;
• Third copy. Child to the second - contains information about data changes since the creation of the second copy.

The advantage of this method of backup data storage, in comparison with the first, smaller size copies (each new incremental copy weighs tens or hundreds of megabytes, depending on the number of changes that have occurred). Minus - the appeal of each new copy to the previous one during recovery. That is, if one of the copies is damaged, you will have to restore to the last working copy in a continuous chain from the first. In addition, restoring from an incremental backup takes longer than from other backup methods.

Differential backup

The differential copy method is close to the incremental copy method, but there is a key difference between them. Within differential copying, new snapshots are children of the first one.

This means that during the first backup using the differential method, a complete copy of the system is created, after which all subsequent snapshots contain information about the changes that have occurred from the first copy. It looks something like this:

• First copy. Main - contains all the information;
• Second copy. Child - contains information about data changes since the creation of the first copy;
• Third copy. Child - contains information about data changes since the creation of the first copy.

As you can see, the third copy in the differential backup method is not a child of the second. That is, if there are problems with one of the differential snapshots, it will be possible to restore to any other working differential copy. This is the key difference between differential and incremental backups.

Each differential snapshot is larger than the incremental snapshot because it needs to store information about all changes since the first full backup was taken. In this case, each new differential image will weigh more than the previous one.

Which backup method is best

After considering three backup methods, each user can independently decide which option is best for him. Let's briefly summarize and give a few scenarios:

• Full backup. Most reliable way. Suitable for those users who have the ability to store large backups;
• incremental backup. The best option for users who back up to a small disk such as an SSD. The advantage of this method, compared to differential backup, is only in the size of each new system snapshot;
• Differential backup. The best option for home computer users. With this method of copying, you only need to take care of the safety of the first copy.

Types (types) of backup differ in many ways. In this article, we will look at the main backup algorithms, carry out short review each of the traditional and new types of backup. We will show how they differ, as well as list the advantages and disadvantages of each of them.

Full Backup: FULL BACKUP

This method creates a complete copy of the original data set, therefore it is the best protection option in terms of data management and speed of data recovery. But this method takes many times longer than other backup methods, and also creates a significant network load.

Usually, full backups are taken periodically and combined with other types of backups.

Benefits of Full Backup:

• fast recovery data
• simple control
• all data is contained in one backup copy

Disadvantages of Full Backup:

• requires a lot of storage space for backups
• lengthy backup

Differential Backup: DIFFERENTIAL BACKUP

Differential backup type is an intermediate solution between full backup and incremental backups. Similar to incremental backup, Starting point for a differential backup is to create a full backup and back up only changed data. However, unlike incremental backups, a differential backup does not store the data that has changed since the last backup, but the data that has changed since the original full backup. Thus, a full backup is a constant reference point for successive backups.

A differential backup allows you to restore data faster than an incremental backup because it requires only two parts of the backup: the full backup and the latest differential backup. The backup/restore speed is somewhere between full and incremental backup method. A backup is faster than a full backup, but slower than an incremental backup. Recovery is slower than a full backup, but faster than incremental backups. The amount of memory required for differential backup is at least certain period less than what is required for a full backup and more than what is required for an incremental backup.

Benefits of Differential Backup:

• backup is faster than full but slower than incremental
• recovery is faster than incremental, but slower than full
• a more reliable way (recovery only requires a full and latest backup)

Disadvantages of Differential Backup:

• each subsequent backup takes longer and takes longer disk space in storage

Incremental Backup: INCREMENTAL BACKUP

An incremental backup uses a full backup as a starting point. It then backs up only the blocks of data that have changed since the last backup job, at the specified job run time. Depending on the backup retention policy, a new full copy is created after a certain period to repeat the cycle.

Imagine that on Sunday we made a full copy of the data, on Monday we make a copy of the data that has changed since the full copy. On Tuesday, only the data that has changed since Monday, and so all the days until Sunday, and on Sunday we make a new full copy. In this way, incremental backups can be performed as often as required, as only copies are kept. recent changes. Incremental backup allows you to reduce the amount of data transferred, thereby reducing backup execution time and reducing network load. Backups are fast and require much less storage space than full backups, but the restore process takes longer because both the full backup and the entire chain of consecutive blocks need to be restored. If at least one block in the chain is missing or corrupted, it may not be possible to restore.

Benefits of Incremental Backup:

• high backup speed (only blocks of changed data are copied)
• less storage space (compared to full)
• more restore points

Disadvantages of Incremental Backup:

• low speed data recovery (it is necessary to restore both the initial full copy and all subsequent blocks)
• less reliable (depends on the integrity of all blocks in the chain)

Reverse Incremental Backup: REVERSE INCREMENTAL BACKUP

A reverse incremental backup, similar to other types of backups, starts with a full backup, but with each new backup, all data from the previous (full) backup is moved to the new backup, and the previous RC is replaced by an increment. Thus, the difference of this type is that the latest (newest) backup is always full, while older backups, on the contrary, always have increments. This enables faster recovery, as the most recent backup is often the most valuable and in-demand.

In contrast to the reverse, with a regular incremental backup, the last backup depends on all the previous ones, so it takes more time to restore data (since not one, but several backups are involved in the process), and also if at least one copy is damaged, recovery data will not be possible.

Benefits of Reverse Incremental Backup:

• quick restore (for latest backups)
• higher data security
• more flexible storage volume management (buckup repository). If there is not enough space, you can delete old versions of backups without consequences
• low network load (as for a regular incremental RC)

Disadvantages of Reverse Incremental Backup:

• higher requirements for the backup server
• more time to restore old copies

Synthetic Full Backup: SYNTHETIC BACKUP

A synthetic backup has a lot in common with a reverse incremental backup type. The difference is that the previously created full and incremental backups are used to create a new full backup. Synthetic backup, like the other methods, starts with a full backup, followed by a series of incremental backups. At a given moment, the existing full backup and increments are merged (synthesized) into a new full backup, this new copy will become the source for creating the next increments, and so on. The synthetic type of backup has the same advantages as a full backup, but at the same time solves its shortcomings, loads the network less and saves storage space for the backup.

Benefits of Synthetic Full Backup:

• high speed backup and restore
• flexible data management
• low network load (to receive incremental RCs)

Disadvantages of Synthetic Full Backup:

• higher load on the backup server
• in some cases licensed as a separate option

Conclusion

We've covered the basic backup methods. When choosing a backup type, consider the pros and cons of each. individual cases, based on the data protection policy, storage volume, computing resources, throughput networks, service level agreements, critical data areas, and so on.

What is an incremental backup?

Incremental backup.
Copy only new and changed files.

incremental backup (incremental backup) is a type of differential backup, when not all source files are copied, but only new and modified from the moment the previous copy was created - full or incremental. This significantly saves disk space and greatly speeds up the backup process.

The name of this type of backup comes from the English word incremental backup- additional. In Russian it is called Additional. This type backup is the most common, but like all methods, it also has its pros and cons.

This type of backup is perfect for backing up large amounts of source data, 50 gigabytes or more. The speed of creating backups will be quite high, and the size of each incremental copy can be only 100-200 megabytes.

Pros :

• Quick Creation backup
• Small backup footprint (saving disk space)

Minuses :

• Complexity of setup (compared to a full copy of Full Backup)
• Difficulty in restoring files (compared to a full copy)

Conclusion: Create incremental backups if the amount of source data is large and time for copying files and saving disk space matters to you. The optimal frequency of creating an Incremental backup is 1 time per hour, if source files change frequently and 1-2 times a day if the files are rarely edited.

How to make an incremental backup with Exiland Backup

Exiland Backup is a simple utility for backing up and synchronizing folders over the network, FTP, between PCs and servers. Supports all types of file backups.

This universal program well suited for backing up file 1C, sites on Wordpress and other CMS, copying site files from an FTP server to a local PC.

After launch, in the main window of the program, on the top of the panel, click the button for creating a new task, specify the name of the task, for example, "My Documents" and click "Next". Now, as shown in the screenshot below, select the copy type "Incremental".

Screenshot of the program. Select the type of copy.

There is an option below to limit the number of full copies so that the oldest backups are automatically deleted before a new full copy is created. This setting saves disk space (not available in Free version). You can also limit the number of incremental copies between full. When this limit is reached, another full copy will be created.

When choosing a backup naming template, you can add a string such as "(incremental)" for incremental backups to visually distinguish them from full backups.

When the task is created, you do not have to wait for the start time - you can start the task manually by clicking on the "Run" button located on the top panel.

Michael, software developer

Other types of copying.

Greetings, dear site visitors! Let's continue the topic we started in the last post of this section and this time we will take a closer look at how incremental backups are performed.

Each data block in the data file contains a system change number (SCN), which is the SCN on which the new change in the block was made. During an incremental backup, RMAN reads the SCN of each block of data in the input file and compares it to the SCN checkpoint parent incremental backup. If the SCN in the input data block is greater than or equal to the SCN of the parent's checkpoint, then RMAN copies the block.

Note that if you enable the block change tracking option, RMAN can refer to the change tracking file to identify changed blocks in data files without scanning the entire contents of the data file. Once enabled, block change tracking will not affect how you perform or use incremental backups, it only offers improved performance.

Incremental Backups Tier 0 and Tier 1

Incremental backups can be level 0 or level 1. A level 0 incremental backup, which is the basis for subsequent incremental backups, copies all blocks containing data, backing up the data file to the backup set, just like a full backup. The only difference between a level 0 incremental backup and a full backup is that a full backup is never included in an incremental strategy.

A level 1 incremental backup can be one of the following types:

• A differential backup that backs up all blocks modified since the last incremental backup at level 1 or 0
• A cumulative backup that backs up all blocks changed since the last incremental backup at level 0

Incremental backups are differential by default.

The size of the backup file depends solely on the number of modified blocks and the level of incremental backup.

Differential Incremental Backups

In a level 1 differential backup, RMAN backs up all blocks that have changed since the last cumulative or differential incremental backup at level 1 or 0. RMAN determines which level 1 backup was last and backs up all blocks modified since that backup. If no level 1 backup is available, RMAN copies all blocks changed since the level 0 backup.

The following command performs a Level 1 differential incremental backup of a database:

RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE;

If a level 0 backup is not available, then the behavior depends on the compatibility mode setting. If compatibility is >=10.0.0, RMAN copies all blocks changed since the file was created and saves the results as a level 1 backup. In other words, an SCN equal to the file's creation SCN is taken during an incremental backup. If compatibility<10.0.0, RMAN генерирует бэкап уровня 0 содержимого файла во время резервного копирования, чтобы не было противоречия с предыдущими релизами.

Figure 1 Differential Incremental Backups (default)

• On Sunday
  Level 0 incremental backups all
• Monday through Saturday
  Every day from Monday to Saturday, a level 1 differential incremental backup backs up all the blocks that have changed since the last incremental backup at level 1 or 0. So, a Monday backup copies blocks that have changed since a Sunday level 0 backup, a Tuesday backup copies blocks , changed starting backup level 1 on Monday 1, etc.

Cumulative Incremental Backups

In a level 1 cumulative backup, RMAN backs up all the blocks that have been used since the last level 0 incremental backup. Cumulative incremental backups reduce the work required for restores by ensuring that you only need one incremental backup from any given level. However, cumulative backups require more space and time than differential backups because they copy the work done by previous backups at the same level.

The following command performs a level 1 cumulative backup of the database:

BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE; # blocks changed from level 0

Figure 2 Cumulative Incremental Backups

In the example shown on , the following happens:

• On Sunday
  Level 0 incremental backups all blocks that have ever been used in this database.
• Monday through Saturday
  A cumulative incremental level 1 backup copies all blocks that have changed since the last level 0 backup. Since the last level 0 backup was taken on a Sunday, a level 1 backup every day from Monday to Saturday backs up all the blocks that have changed since the Sunday backup.
• The cycle repeats over the next week.

A Simple Incremental Backup Strategy

Choose a backup scheme according to an acceptable MTTR (short for mean time to recover). For example, you can implement a three-tier backup scheme so that a full or level 0 backup is taken monthly, a cumulative level 1 backup is taken weekly, and a differential level 1 backup is taken daily. In this scheme, you will never have to apply more than one day's stock of transaction logs for a full recovery.

When deciding how often to take a full or level 0 backup, a good rule of thumb is to take a new level 0 backup every time 50% or more of the data has changed. If the rate of change in your database is predictable, then you can monitor the size of incremental backups to determine when to take the next level 0 backup. The following query displays the number of blocks written to the backup set for each datafile with at least 50% its reserved blocks:

SELECT FILE#, INCREMENTAL_LEVEL, COMPLETION_TIME, BLOCKS, DATAFILE_BLOCKS FROM V$BACKUP_DATAFILE WHERE INCREMENTAL_LEVEL > 0 AND BLOCKS / DATAFILE_BLOCKS > .5 ORDER BY COMPLETION_TIME;

Compare the number of blocks in differential or cumulative backups with a level 0 base backup. For example, if you create only level 1 cumulative backups, then after taking the next new level 1 backup with a size of approximately half the size of the level 0 base backup, take a new level 0 backup 0.

Thank you for your attention!.