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Repository Storage

This section refers to the sizing of standard disk repositories.

Best Practice

  • The Restore Point Simulator sizer can be used to estimate capacity requirements: RPS Calculator
  • Use of ReFS can reduce the space requirements for synthethic fulls and GFS

Estimating Repository Capacity

When estimating the amount of required disk space, you should know the following:

  • Total amount of data being backed up
  • Frequency of backups
  • Retention period for backups
  • Will jobs use forward or reverse incremental
  • If ReFS formatting be used

Also, when testing is not possible beforehand, you should make assumptions on compression and deduplication ratios, change rates, and other factors. The following figures are typical for most deployments; however, it is important to understand the specific environment to figure out possible exceptions:

  • Data reduction thanks to compression and deduplication is usually 2:1 or more; it’s common to see 3:1 or better, but you should always be conservative when estimating required space.
  • Typical daily change rate is between 2 and 5% in a mid-size or enterprise environment; this can greatly vary among servers; some servers show much higher values. If possible, run monitoring tools like Veeam ONE to have a better understanding of the real change rate values.
  • Include additional space for one-off full backups.
  • Include additional space for backup chain transformation (forward forever incremental, reverse incremental) – at least the size of a full backup multiplied by 1.25.
  • Using ReFS formatting will dramatically reduce space requirements for synthetic full and GFS through the Fast Clone feature.

Note: When using deduplication appliances, please use vendor specific sizing guidelines.

Using the numbers above, you can estimate required disk space for any job. Besides, always leave plenty of extra headroom for future growth, additional full backups, moving VMs, restoring VMs from tape.

A repository sizing tool that can be used for estimation is available at RPS Calculator. Note that this tool is not officially supported by Veeam, and it should be used “as is”, but it’s nonetheless heavily used by Veeam Architects and regularly updated.

Tip: With Veeam Availability Suite, you can use Veeam ONE together with Veeam Backup & Replication. Among the many reports, Veeam ONE has the VM Change Rate Estimation report from the “Infrastructure Assessment” report pack; this can be used as an indicative pre-deployment assessment of the potential amount of space that should be available on the backup repositories. This report is built measuring the number of VM virtual disk write operations supplied by VMware vSphere while additional compression and deduplication (usually 2 to 3 times) ratio should be assumed.

It is also recommended to periodically run the “Capacity Planning for Backup Repositories” report from the “Veeam Backup & Replication Reports” pack to analyze the amount of free space on backup repositories and estimate the projected growth and consequent space consumption. The report provides recommendations for adjusting the allocated storage resources in order to meet the future demand for backup storage. Furthermore, it calculates the amount of additional space that needs to be provisioned to accommodate the necessary restore points.

DAS or SAN?

Direct-Attached Storage (DAS)

This is an easy, fast and lowcost way to use storage. It is a new approach to use microsegmentation instead of monolithic solutions. The DAS approach is in terms of performance a very fast solution. It can be used as a dedicated system to one cluster or in a Scale-out Backup Repository. DAS is a normal industry standard x64 server with a bunch of disks attached to it.

  • It is recommended to use a performant RAID controller with local battery cache. Be aware of any RAID overhead when designing a DAS soltuion. Typically RAID 6/60 (depends on the amount of disks) is recommended (IO overhead of factor 6). The stripe size should be 256KB or greater.
  • Since a DAS storage can be fully dedicated to backup operations, this type of repository is considered to offer a good balance between “performance” and “cost” factors.
  • A strong benefit of a DAS repository is that it supports the features offered by Veeam Backup & Replication in a very flexible way. In particular, it provides good read and write performance, sufficient for Veeam vPower-based features (such as Instant VM Recovery, SureBackup, and others). As it typically provides good random I/O performance, it will be the optimal solution when using I/O intensive backup modes such as reverse incremental or forever forward incremental (also used in backup copy job).
  • For scalability you can scale vertical (more disks in an enclosure or additional) and horizontal (more servers, if e.g. the network throuput is reached, the SAS channels are saturated, more IOPS are needed for restore reasons)

Tip: When using Microsoft based repositories, use the RAID controller, to build the RAID set and set the stripe size there. Don’t use any kind of software or HBA based RAID level.

Pros Cons
Cheap RAID Controller is a single point of failure
High performance  
Simplicity  
Microsegmentaion  

SAN Storage

This is an advanced and manageable solution that offers the same advantages as DAS, and adds more advantages like higher availability and resiliency.

The volume size and quantity are easily adjustable over time, thus offering a scalable capacity.

Tip: You can configure multiple backup repositories on the SAN storage to increase repository throughput to the storage system.

Pros Cons
Reliability Complexity
Performance Expensive
Technical capabilities Monolithic approach

References