MichaelC,
What may be occuring is one or more PG's have a different long term retention range. DPM will only co-locate protection groups that have the same protection range, so more tapes would be used under that condition.
Also offsite ready get flagged according to a combination of variables.
Rotating Tapes Offsite
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DPM Administrator Console indicates when a tape in the library should be removed and stored in your archive location by displaying a green icon in the Offsite Ready column. You can also view all tapes ready to be stored offsite in the Tape Management Report.
The Tape Management Report lists tapes that will be due for offsite storage in the upcoming period of time selected for the report.
When the data on a tape expires, return the tape to the tape library. Expired tapes not returned to the tape library will be marked as "overdue" in the Tape Management Report. Overdue tapes expired during an earlier reporting period. Expired tapes should
be returned to the tape library for reuse.
DPM 2007 - http://technet.microsoft.com/en-us/library/cc964296.aspx
DPM 2010 - http://technet.microsoft.com/en-us/library/ff399230.aspx
When tape colocation is enabled, a tape on to which offsite backup is written will not be shown as Offsite Ready unless one of the following conditions are met:
- The tape is full.
- One of the datasets has expired.
- Write-period ratio has been crossed. (By default, this is first backup time + 15 per cent of retention range.)
TapeWritePeriodRatio is not a registry. It is a global property for the DPM which needs to be set using DPM CLI command. Here is the command to set it
Set-DPMGlobalProperty –DPMServerName <dpm server name> -TapeWritePeriodRatio <fraction>
WritePeriodRatio:
TapeWritePeriodRatio is a property that can be set when colocation is enabled on tape. In case of non-colocated ProtectionGroup, the tape becomes marked as “offsite ready” as and when it is written on to.
Colocation is enabled for PGs of identical retention periods. However the times at which data are backed to tape may vary for each collocated PG. In such cases, this parameter helps the user to decide how long to write to tape before sending the
tape offsite, even though it might not be full.
WritePeriodRatio indicates the number of days for which data can be written on to a tape as a ratio of the retention period of the first data set written to the tape.
WritePeriodRatio value can be between 0.0 to 1.0
Default value is 0.15 (i.e. 15%)
For example, if the retention period for the first data set written to a tape is 100 days, and you set the Write-Period ratio as 0.15, data will be written to the tape for 15 days from the day on which the first data set was written to the tape. After this
period, the tape will be marked as offsite ready and no more data will be written to that tape until all recovery points have expired on that tape.
Additionally - if OptimizeTapeUsage property is set to true and if CurrentTime > First Dataset’s CreationTime + (WritePeriodRatio * RetentionRange of First Dataset) then no data will be written on to the tape till all datasets on tape are expired.
TapeExpiryTolerance:
indicates the number of days over the furthest expiry date among all datasets on the tape that the tape will continue to be used.
The default value is 10 percent.
These registry values are located under HKLM\Software\Microsoft\Microsoft Data Protection Server\1.0\Colocation.
The OptimizeTapeUsage parameter should be set to True to set TapeWritePeriodRatio for a DPM server.
The value can range from 0 - 1.
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ExpiryToleranceRange Indicates the time window within which the expiry date of the dataset to be written to the tape must fall. It is expressed as a percentage. The default value is 17 percent.
This is a DWORD type registry value located under HKLM\Software\Microsoft\Microsoft Data Protection Manager\1.0\Colocation. DPM does not create this key automatically. You must manually create this key if you want to set the ExpiryToleranceRange.
For ExpiryToleranceRange:
It is used in the calculation of the time window as follows:
Let, Furthest expiry date among the expiry dates of all the Datasets already on the tape = FurthExpDate
Time Window =
FurthExpDate - TapeExpiryTolerance* (FurthExpDate –today’s date) (Lower Bound)
FurthExpDate + TapeExpiryTolerance* (FurthExpDate –today’s date) (Upper Bound)
So, the current dataset will be co-located on the given tape only if its expiry date falls within Time Window (both bounds inclusive)
For TapeWritePeriodRatio:
This parameter governs the time period for which DPM is able to go on adding Datasets to a co-located tape. It is expressed as a fraction between [0-1]. It is used in the calculation of the Time Limit as follows:
Let, Earliest backup time among any of the datasets on the media = FirstBkUpTime
Time Limit = FirstBkUpTime + WritePeriod Ratio*RetentionRangeOfFirstDataset
So, a dataset will go in a co-located tape only if the current time is less than the Time Limit as defined above.
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Hope this help
Regards, Mike J [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
