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Setting Up the Dell DR Series System as an RDA or VTL Backup Target for Dell NetVault Backup
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 NOTE: 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.
A.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 resul
ts 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 disparit
ies 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.
In the previous example at the end of the 5-week cycle the 1
st
week retires and frees up media to be reused or
recycled which once processed will allow the DR to reclaim the physical space associated with the virtual
media. Since the smallest data set footprint resulting from the change rate is 2TB in each incremental iteration
we create our media at 800GB increments and add as we grow. For this example the initial Virtual Tape
Library would be created with 152
( 121TB divided by 800GB ) pieces of media at 800GB for each piece media.
20TB Total initial footprint with a 10% change rate