DPM default space allocation formulas
When protecting a Data Source in DPM, you have the option to define your own Replica Volume and Recovery Point Volume sizes or to use the default sizes determined by DPM. Typically, the default sizes provide significant room for growth without gross overallocation of resources (though I tend to find they allocate more space than necessary…I prefer to manually allocate slightly more than the Data Source size and run an “autogrow” script to thin-provision resources. You can find out how to autogrow space here). Below are the algorithms used by DPM to determine how much space to allocate to a Data Source.
Replica volume
For files: (Data source size x 3) / 2 For Exchange data: Data source size x (1 + log change) / (alert threshold - .05) <strong>Note: </strong>Log change is assumed to be 6%. Alert threshold typically 90%. For SQL Server data: Data source size x (1 + log change) / (alert threshold - .05) <strong>Note: </strong>Log change is assumed to be 6%. Alert threshold typically 90%. For Windows SharePoint Services data: Total size of all databases/ (alert threshold - .05) <strong>Note: </strong>Log change is assumed to be 10%. Alert threshold typically 90%. For Virtual Server data: Data source size x 1.5 For system state: (Data source size x 3) / 2 <strong>Note:</strong> Data source size is assumed to be 1GB for Windows 2003 and 10GB for Windows 2008
Recovery point volume
For files: (Data source size x retention range in days x 2) / 100 + 1600 MB <strong>Note: </strong>Retention range is assumed to be 5 For Exchange data: 4.0 x retention range in days x log change x data source size + 1600 MB <strong>Note: </strong>Log change is assumed to be 6% and retention range is assumed to be 5 For SQL Server data: 2.5 x retention range in days x log change x data source size + 1600 MB <strong>Note: </strong>Log change is assumed to be 6% and retention range is assumed to be 5 For Windows SharePoint Services data: 1.5 x retention range in days x log change x total size of all databases + 1600 MB <strong>Note: </strong>Log change is assumed to be 10% and retention range is assumed to be 5 For Virtual Server data: (Data source size x retention range in days x 0.02) + 1600 MB <strong>Note: </strong>Retention range is assumed to be 5 For system state: (Data source size x retention range in days x 2) / 100 + 1600 MB <strong>Note: </strong>Retention range is assumed to be 5
Change journal (for file protection only)
300MB stored on each volume on the protected server
When you are creating a Protection Group (or adding a Data Source to an existing Protection Group), in the modify disk allocation dialog box, these are the algorithms that are used to determine the initial disk allocation based on the volume that the Data Source is on. To apply these algorithms to the actual Data Source, click the calculate button and DPM will poll the client and determine the actual Data Source allocation based on that particular Data Source size and its corresponding formula (which can take a while).
Keep in mind that once you allocation space to a Data Source and commit the settings, you cannot decrease the space allocated. The only way to remove space from a Data Source is to remove protection for it and then setup protection again.
Tags: DPM
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