How Often Should I Back Up?

How Often Should I Backup?

Now that you understand your organization's data protection requirements and have the necessary tools to implement them, you need to design the schedules for your backups. If you have little data or a high budget for backups, you'll use multiple schedules. You'll use three metrics:

• Value
• Change frequency
• Application characteristics

Understanding How Data Value Affects Backup Scheduling

The frequency of your full backups directly determines how many data copies you'll have over time. The more copies you have of any bit, the higher the probability that at least one copy survives a disaster. Therefore, if you have data that you can never afford to lose, your program should reflect that.

Understanding How Change Frequency Affects Backup Scheduling

Data that changes frequently may need to be backed up just as often. As you remember from the first section, recovery point objectives (RPO) set the maximum time between backups and determine how much recent data you could lose. Additionally, you should consider how often this data changes independently of the RTO.

If you have data that rarely changes, you can consider a longer RPO. If you only change an item every few months, backing up weekly may not make sense. However, this could have unintended consequences.

For example, you set a monthly schedule for your domain controller because personnel turnover is rare and you only replace a few computers per year. Then, you hire a new employee and provide them with a computer the day after a backup.

If something happens to Active Directory this month, you'll lose all of this new information. Your program needs to consider such possibilities.

Understanding How Backup Application Features Affect Scheduling

Modern commercial backup applications share many common points. They all have a way to plan your tasks. Each uses a method to optimize backups. The full features of the solutions you use will affect your scheduling.

The following list provides a starting point for determining how to take advantage of the features in your selected program:

Virtual Machine Awareness

If your backup software understands how virtual machines are backed up, it can process efficient sequencing. Otherwise, you'll need to schedule backups of guest operating systems to avoid overloading your resources.

Space-Saving Features

If your backup tool can save storage space, there are obvious benefits. Everything involves trade-offs — make sure you know what you're giving up for that extra space.

Some common points to consider:

• Traditional differential and incremental backups complete faster than the full backups they depend on. They don't mean anything without full backups. Design your program to include full backups as much as time and space allow;
• More recent delta and data deduplication techniques provide more space savings than differential and incremental methods, but they require additional computation and monitoring beyond the necessary full backups. They shouldn't use too much CPU time, but you'll need to test them. Also, check whether your application tracks changes and how it does so. Some take up space on your active disks;
• If you have extra space in your storage environment, don't become overly dependent on these technologies. Create more full backups if possible.

Time-Saving Features

Most of the features mentioned earlier save time and space. As with space, try not to save time you don't need.

Replication

Replication functions require bandwidth and can cause serious performance issues when going through Internet connections. If a replication job doesn't complete before the next job starts, you may end up with unusable backups.

Environment Types

Because of large performance differences among various backup environment types, your selected option(s) determine how you'll schedule backups and which space-saving features to use. For example, if you need to back up several terabytes to a band and a full backup takes twelve hours to complete, you can only run the full backup when you have twelve hours available.

Snapshots Features

If your backup application integrates with VSS (Volume Shadow Copy Service - a feature of the Windows Operating System) or uses another technique to get consistent or application-consistent backups, you'll have more scheduling options.

Backups use system resources and you don't want one job to interfere with another, but snapshot acquisition allows you to run backups while the systems are in use.

You should know your backup program well during the deployment phase. Take time to fully understand how your backup program works. Don't forget the need for periodic full backups.

Taking Action

Taking a full backup every time will quickly exceed any rational amount of time and media, so you'll have to make trade-offs. Remember that, if possible, you'll get a full backup of all your data at least once per day.

Guidelines for Backup Scheduling:

• Full backups require time and resources, even with continuous snapshot technologies. Try to schedule them during periods of low activity.
• Full backups are not dependent on other backups. Therefore, they have the greatest value after major changes. For example, some organizations have complex end-of-month procedures. Taking a backup immediately afterward can save a lot of time in the event of a restore.
• Incremental, differential, delta, and deduplicated backups require relatively less time and space than full backups, but they are dependent on other backups. Use them as filler between full backups.
• If your backup plan primarily uses online storage space, make sure to schedule backups to offline media. If this is a manual process, implement an accountability plan.
• Administrators tend to schedule backups and system and software updates at night. Make sure the schedules don't conflict.

Grandfather-Father-Son Example Plan

"Grandfather-Father-Son" (GFS) schemes are very common. They work best with rotating environments like tapes. A typical example schedule:

• "Grandfather": A full backup is taken once a month. The grandfather media is rotated yearly (i.e., write the January 2021 backup over the January 2020 tape, February 2021 over February 2020, etc.). A grandfather type is taken once a year, usually the type that follows your organization's fiscal year-end, and never overwritten in accordance with your data retention policy.
• "Father": A full backup is taken weekly. The father media is rotated monthly (i.e., a "Week 1" tape, a "Week 2" tape, etc.).
• "Son": Incremental or differential backups are taken daily and the media is overwritten weekly (i.e., a "Monday" tape, a "Tuesday" tape, etc.).

The above example is not the only type of GFS schema. The relationship between different rotation components determines how they are characterized. You have a long-lasting full media set, a shorter-living full media set, and a media that rotates quickly.

Some applications don't keep yearly media. Others don't rotate monthly full backups, instead keeping full backups for the entire retention period. Some don't rotate daily media every week. Your organization's needs and budget determine your implementations.

With a GFS schema, you'll never be further away from a full restore than a few media pieces. Remember that a backup in the "differential" style needs the latest "son" media and the immediately preceding "father," while a backup in the "incremental" style needs the latest "father" media and all the "sons."

A disadvantage of a GFS plan is that you lose detailed levels of daily backups quickly. When rotating daily, anything written over will live at best in the latest monthly or maybe even yearly backup. The greatest risk is data created and deleted between full backup cycles.

Online Media Example Plan

If your backup solution primarily uses online media, the respected GFS approach may not work well. Most systems that are always online don't have the same "rotation" concept. Instead, they use a structured retention policy that trims old data when it reaches its end-of-life period.

For these, your configuration will depend on how your backup program stores data. If it uses a deduplication schema and keeps only one full backup, there won't be much you can do other than configure the backup frequency and retention policy.

Continuous Backup Example Plan

Many applications have a kind of "continuous" backup. They capture data with extremely small time increments. For example, Hornetsecurity's VM Backup has a "Continuous Data Protection" (CDP) feature that allows you to set a scheduling interval as short as five minutes.

Scheduling these types of backups involves three important points:

• How does your backup application store "continuous" backup data?
• How fast do the protected data change?
• How much do the protected data change within the target time period?

If your backup program takes full, independent copies at every interval, your media space may deplete very quickly. If it uses a deduplication type storage mechanism, it should use much less. In both cases, your data loss rate will determine how much space you need.

In systems with very high change rates, your backup system may not have enough time to complete a backup before the next one starts. This can lead to serious problems, most importantly, not being able to provide the continuous backup you want.

You can easily predict how some systems will behave; others require more effort. You may need to spend some time adjusting a setting, observing how it performs, and adjusting it again.

Hybrid Backup Plan Example

You don't need to create a single program that works for everyone. You can set different programs. Use your RTOs, RPOs, retention policies, and capacity limits as a guide. One possibility:

• Domain controllers: Standard GFS with one-year retention
• Primary business application server (only application): Monthly full, scheduled after OS and software updates, with three-month retention
• Primary business database server: Continuous, six-month retention
• Primary file server: Standard GFS with five-year retention
• Email server: Specialized in Exchange, daily full, hourly differential, different backup program with five-year retention
• All: Copied to a remote site every night at midnight
• All: Monthly full offline according to retention policies

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Source: How Often Should I Backup? (hornetsecurity.com)