Properly Sizing a Datto Appliance

Topic

This article discusses how to choose the appropriate size when buying or upgrading a Datto device.

Environment

  • Datto SIRIS
  • Datto ALTO
  • Datto NAS

Description

This article will help you size a Datto Business Continuity and Disaster Recovery (BCDR) appliance to meet your data backup needs. We recommend that you review the information presented here before you upgrade or purchase a Datto appliance.

Storage space considerations

When qualifying organizations for a Datto appliance, it is essential to consider both current and future storage requirements.

  • The number of production machines and NAS shares that you need to protect.

  • The size of each of the protected machines.

  • The amount of block-level change the system willproduce. Take into account databases, separate database backups, log files, application, and files change daily.

  • Encrypted agents, if used, should be treated as uncompressed and will take up more space.

  • The types of files being backed up. Certain file types cause substantial changes when accessed for utilization or updating. Large databases, media files, or production workspaces can have large sizes and thus larger backup images.

NOTE  We recommend that you overestimate this number since, while block-level changes are primarily caused by file change, other factors such as disk sector changes are also involved.

Backup frequency and time-span considerations

Different server roles require different backup frequencies for proper protection. Typical requirements are as follows:

  • Exchange servers: hourly backups
  • Terminal servers: daily backups
  • Auxiliary domain controllers: several backups per week

Other variables to consider:

  • The amount of time the backups will need to be stored.
  • In the case of a Disaster Recovery, the amount of time the protected machine may need to be virtaulized on the Datto appliance
  • If the organization have expansion plans in place, which may include additional servers or workstations.

Datto hardware resource limitations

Datto appliances must have adequate resources to perform both daily tasks (such as taking backups) and ad hoc, resource-intensive operations (such as a local virtualization). Low system resources can severely affect local virtualizations, as the virtualized machines will seek resources that are not physically available. This can lead to virtual machines running slowly, or high-resource programs crashing.

For example, an organization has a single server environment (Small Business Server) running all the organization's daily operations. The server has the following hardware specifications and conditions:

  • Quad-core CPU and 32 GB of RAM
  • Storing an average of 525 GB of data on its HDD

If sizing the appliance on storage alone, the SIRIS S3B1000 appliance seems to accommodate the space of the server, as it:

  • Fits within the 2-3x multiplier
  • Provides ample space for data growth

However, if the server goes down and organizations need to run off of a virtualization, the resources available may not be able to power the machine in a sufficient state to allow for operations to continue.

Datto best-practices

This document is only to be used as reference for what is common practice, not what is required or what device limits are. There are numerous configurations that increase or decrease the activity of a device over 24 hours (tighter backup schedules, higher quantity of offsite replication, frequent or long running screenshots, using encrypted agent datasets, etc.).

Performance issues like backups falling behind, delays in screenshot results, or slower performance on disaster recovery can result from taxing configurations after a certain agent count. For general guidance, we've provided the average number of agents per device type.

Please keep in mind these are just rough estimates provided as a guideline. Usage of devices by agent quantity can vary greatly depending on how the device and agents have been configured, whether the agents are encrypted, and the amount of data being protected.

Device capacity Approximate agent count
1TB 2
2 to 4TB 4
4 to 6TB 10
10 to 12TB 15
18 to 24TB 20
24 to 36TB 25
36 to 48TB 40
48 to 60TB 45
60TB or larger 55

Datto's recommended appliance size is twice the total of the used disk space on the protected machine. This best-practice is called the 2-3x multiplier rule, and it ensures the following conditions are always met:

  • The Datto appliance has ample storage available for the first backup of the protected system (the base image, which will be a full disk snapshot)
  • The device can continuously roll this base image to the front of the chain with each incremental backup
  • The Datto appliance has storage space for backups based on the Datto recommended retention policy.

Encrypted Agents: Backups of encrypted agents are stored uncompressed and use more system resources. If you are planning to use encryption to protect your agents, It may be advisable to use a 3X multiplier when determining device size.

Virtualizations: The Datto appliance should have adequate resources for local virtualization of agents, as well as space for at least one additional base image, if needed post restore, for the largest protected machine.

  • When an agent is virtualized on the appliance or in the cloud, the Datto solution can back up the virtualized system with the same agent pairing.

  • This would cause a larger backup to take place, because of the change during restoration, potentially even a full backup. Another would take place once the machine is fully restored.

  • If the local virtualization has the Rescue Agent option enabled (and the normal agent is paused), the rescue agent can continue incremental backups.

Unexpected data growth: There is a slight safety buffer in storage size for cases in which mild unexpected data growth could potentially occur over time. When a Datto appliance's primary storage space reaches maximum capacity the optional resolution paths may be more difficult.

Frequently Asked Questions

The following problems result from not having enough space on your Datto appliance:

  • It fills quickly after deployment, blocking future backups.
  • It cannot maintain local and off-site backup chains.
  • Returning to the previous state after a Disaster Recovery may not be possible wile retaining the current backup chains.

While Datto Technical Support may be able to provide a temporary remedy, issues stemming from a lack of free space will return until space is freed on the appliance, or it is upgraded.

  1. Access the Device Overview page.

  2. Use the Loal Storage Usage graphic and list to assess the size of all protected machines on your Datto appliance and the remaining local free space.

If you experience failed local backups and are constantly modifying local backup retention to keep your system protected, it may be time to upgrade your appliance.

As a rule of thumb, if your appliance is utilizing 85% or more of its local storage from backup storage, or if you do not have enough space to take a new full backup of your largest agent, it may be time to consider upgrading options.

A small organization network has four machines that need to be protected:

  • Exchange Server: 250 GB
  • Application Server: 45 GB
  • Terminal Server: 60 GB
  • Workstation: 100 GB

The total protected space totals 455 GB. This is on the border of an appliance with a terabyte of storage. For local backups, this should be a suitable purchase. There are considerations to take into account:

How long will they maintain local data?

  • Do they have enough upstream bandwidth to get the images synced with the cloud consistently? Delays in offsite replication can effect retention schedules.
  • The recommendation is to have a minimum of 100 Kb/s upstream on a consistent, uninterrupted basis per terabyte of local storage. More is always advisable.

What if they had to restore the Exchange Server? How would this impact space?

  • If the Exchange server goes down and needs to be backed up from a temporary virtualized environment or from a new production host, post restore, the next backup may need to be a full image.
  • Factor in the next Exchange backup being 250 GB. That will cause the appliance to quickly fill up since an additional base image is present and subsequent incremental changes will take place.
  • This may not be as pressing of a factor for smaller agents, as there is less data to back up should the machine need to be re-based.

If your specific sizing scenario is not covered here, contact your Datto Sales Executive for assistance.