Dell DR4100 Symantec Backup Exec - Setting Up the DR Series System on Symantec - Page 98

Various factors such as total data footprint, change rate, backup frequency and data lifecycle policies will dictate how much physical space will be needed to accommodate the Virtual Tape Libraries within a DR Series environment. In addition, if other container types are hosted these two must be factored into space requirement calculations. As a general rule the following can be used as a reference architecture to determine the basic capacity needed for a given virtual tape library container: 1. Determine Existing Data Set 2. Determine the change rate (Differential) 3. Determine the retention period 4. Calculate the data footprint during the retention period for existing data sets based on a 10-1 deduplication ratio 5. Calculate the data footprint during the retention period for change rate data sets based on a 10-1 deduplication ratio 6. Calculate the ratios within the retention period for each of the data sets 7. Determine the lowest ratio data set to be retired within the retention period and create media of size that closest matches this data footprint so that when a retention period is met the most amount of media is recycled to invoke data reclamation alignment and optimizing media consumption. IMPORTANT: If other containers are being configured to host CIFS/ NFS / RDA or OST, these must also be factored into the planning and management of space. C.2.3 Logical VTL geometry and media sizing The logical size of the VTL including media size and media count should be made such so as to accommodate the existing data footprint targeted for protection. The calculation for such should include the initial footprint, change rate and retention period. It should also take in account the size of both full and incremental data sets. Using the smallest iteration of the data sets to dictate the logical size of the VTL media affords users the ability to retire media in smaller increments which results in high levels of use and also provides the users the ability to conduct operations across smaller objects which results in higher levels of flexibility such as when a restore is needed during backup operations. We can review a typical full weekly plus incremental daily example to demonstrate one method of conducting this calculation. In our example the total logical foot print for the customer environment is 20TB and with a 10% change within a weekly recovery point objective period for a complete weeks' worth of protection we calculate that we will require 22TB of total logical media to retain the data footprint for the given environment for one week. In order to allow for disparities we also include a 10% increase to allow for flexibility in the deployment and use of the VTL which results in a 24.2TB total virtual media requirement for a single weekly retention period. Important Note: Media can always be added as needed. Media cannot however be deleted so care must be taken in order to avoid creating too many media items. 98 Setting Up the Dell™ DR Series System on Symantec™ Backup Exec™ | April 2015