{"id":30649,"date":"2019-10-31T21:36:42","date_gmt":"2019-10-31T18:36:42","guid":{"rendered":"https:\/\/prohoster.info\/blog\/bekap-nagotove-razrushaem-mify-v-chest-prazdnika\/"},"modified":"2019-10-31T21:36:42","modified_gmt":"2019-10-31T18:36:42","slug":"bekap-nagotove-razrushaem-mify-v-chest-prazdnika","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/administrirovanie\/bekap-nagotove-razrushaem-mify-v-chest-prazdnika","title":{"rendered":"Backups Ready: Debunking Myths in Celebration","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"Backups
\n
\nBackup is not a trendy technology that\u2019s touted from every corner. It simply needs to be employed by any serious company, that\u2019s all. At our bank, we back up several thousand servers \u2013 a complex, interesting task, and I would like to share some subtleties about it, as well as typical misconceptions regarding backups.
\n<\/a><\/noindex>
\nI have been involved in this field for nearly 20 years, with the last 2 years at Promsvyazbank. In the early days, I performed backups almost manually with scripts that just copied files. Then Windows introduced convenient tools: Robocopy for file preparation and NT Backup for copying. Eventually, specialized software came into play, primarily Veritas Backup Exec, now known as Symantec Backup Exec. So, I've been familiar with backups for a long time.<\/p>\n

Simply put, backup is the process of keeping a copy of data (of virtual machines<\/a>, applications, databases, and files) on a regular basis for safekeeping. The need for backup usually arises from hardware or logical failures that lead to data loss. The goal of a backup system is to minimize losses from information loss. A hardware failure, for example, can occur due to server or storage failure where the database is kept. A logical failure includes loss or alteration of part of the data, often due to human error, such as accidentally deleting a table or file, or running a faulty script. There are also regulatory requirements for storing certain types of information for extended periods, sometimes up to several years.<\/p>\n

\"Backups
\n
\nThe most typical use of backups is the restoration of saved database copies for the deployment of various test systems or clones for developers.<\/p>\n

There are several typical myths surrounding backups that are long overdue for debunking. Here are the most well-known ones. <\/p>\n

Myth 1. Backup has long been merely a minor function within security or storage systems.<\/h3>\n

\nBackup systems remain a separate class of solutions, quite independent. They are tasked with an extremely important responsibility. Essentially, they serve as the last line of defense when it comes to data integrity. Therefore, backups operate at their own pace and schedule. Daily reports are generated for the servers, with events triggering the monitoring system.<\/p>\n

\"Backups
\n
\nAdditionally, the role-based access model for the backup system allows delegation of certain powers to administrators of the target systems for managing backups.<\/p>\n

Myth 2. When there is RAID, backup is no longer necessary.<\/h3>\n

\n\"Backups
\n
\nUndoubtedly, RAID arrays and data replication are good ways to protect information systems from hardware failures, and with a standby server available, quickly switch over in case the primary machine fails.<\/p>\n

However, redundancy and replication do not protect against logical errors made by users of the system. A standby server with delayed writes might help if the error is detected before synchronization occurs. But if the moment is missed? Only a timely backup can help. If it's known that data changed yesterday, the system can be restored to its state from the day before yesterday, extracting the necessary information. Given that logical errors are the most common, the tried-and-true backup remains a reliable and necessary tool.<\/p>\n

Myth 3. Backup is something done once a month.<\/h3>\n

\nThe frequency of backups is a configurable parameter primarily dependent on the requirements of the backup system. It is entirely possible to find data that rarely changes and is not critically important, the loss of which would not be detrimental to the company.
\nIndeed, such data can be backed up once a month or even less frequently. However, more critical data is saved more often, depending on the RPO (Recovery Point Objective), which defines the acceptable data loss. This could be daily, weekly, or even several times an hour. For us, it's the transaction logs from the DBMS.<\/p>\n

\"Backups
\n
\nWhen systems are put into industrial operation, documentation for backup procedures must be approved, detailing the main points, update regulations, recovery procedures, storage methods for backups, and similar aspects.<\/p>\n

Myth 4. The volume of backups continuously grows and completely fills any allocated space.<\/h3>\n

\nBackups have a limited retention period. For example, it makes no sense to store all 365 daily backups for a year. Typically, daily copies can be kept for 2 weeks, after which they are replaced with newer ones, and the version made first in the month is kept for long-term storage. That version also has a specified retention period\u2014each copy has a lifespan.<\/p>\n

\"Backups
\n
\nThere is protection against data loss. The rule is: before a backup is deleted, the next one must be created. Therefore, data will not be deleted if a backup fails, for instance due to server unavailability. Not only are time frames observed, but the number of copies in a set is also controlled. If the system is designed to maintain two full backups, there will always be two, and the old one will only be deleted when a new third backup is successfully written. Thus, the growth in space occupied by backup archives is solely related to the increase in the amount of data being protected and is independent of time.<\/p>\n

Myth 5. The backup has started\u2014everything has frozen.<\/h3>\n

\nIt\u2019s better to say this: if everything has frozen, it means the administrator's skills are lacking. In general, the performance of a backup depends on many factors, such as the speed of the backup system itself: how fast the disk storage and tape libraries are. From the performance of servers<\/a> the backup system: whether they can process data, perform compression, and deduplication. Additionally, it depends on the speed of the communication lines between the client and the server. <\/p>\n

A backup can occur in one or multiple streams, depending on whether the system being backed up supports multithreading. For example, the Oracle DBMS allows multiple streams based on the number of available processors until the transfer speed is limited by network bandwidth.<\/p>\n

If you try to back up with a large number of threads, there is a chance of overloading the running system, and it will definitely start to lag. Therefore, an optimal number of threads is chosen to ensure adequate performance. If even the slightest decrease in performance is critical, there is an excellent option when the backup is performed not from the production server but from its clone \u2013 standby in database terminology. This process does not load the main working system. Data can be retrieved through more threads since the server is not used for servicing.<\/p>\n

In large organizations, a separate network is created for the backup system so that the backup does not affect the production environment. Moreover, traffic can be transferred not through the network but through SAN.
\n\"Backups
\nWe also try to distribute the load over time. Backups are predominantly done during non-working hours: at night, on weekends. Additionally, they are not started simultaneously. Backing up virtual machines is a special case. The process practically does not affect the performance of the machine itself, so the backup can be spread throughout the daytime rather than postponed entirely to the night. There are many nuances; if everything is considered, backup will not impact system performance.<\/p>\n

Myth 6: I started the backup system \u2013 and there is your fault tolerance.<\/h3>\n

\nNever forget that the backup system is the last line of defense, which means there should be at least five other systems in place to ensure the continuity, high availability, and disaster resilience of the IT infrastructure and information systems of the enterprise.<\/p>\n

It is not wise to hope that the backup will restore all data and quickly bring the crashed service back online. Data loss from the moment of backup to the moment of failure is guaranteed, and data on the new server may take several hours (or days, depending on the situation) to upload. Therefore, it makes sense to create complete fault-tolerant systems rather than relying solely on backups.<\/p>\n

Myth 7: I set up the backup once, checked that it worked. Now I just need to monitor the logs.<\/h3>\n

\nThis is one of the most harmful myths, its falsehood only realized during an incident. Logs of successful backups do not guarantee that everything went as it should. It is crucial to verify the saved copy in advance for deployability. This means running the restoration process in a test environment and checking the results. <\/p>\n

And a bit about the sysadmin's work<\/h3>\n

\nNo one manually copies data anymore. Modern backup systems can back up almost everything; you just need to configure them properly. When a new server is added, you must set policies: choose the content to be backed up, specify storage parameters, and apply a schedule.<\/p>\n

\"Backups
\n
\nNonetheless, there is still plenty of work due to the extensive array of servers, including databases, email systems, clusters of virtual machines, and file resources on both Windows and Linux\/Unix. The staff maintaining the functionality of the backup system are never idle.<\/p>\n

On this holiday, I wish all admins strong nerves, precise movements, and endless space for storing backups!<\/p><\/blockquote>\n

Source: habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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