We have a report with 150k rows and 3 levels of grouping, roughly 150k groups in level 1, and the second level contains 1-3 groups, and each of those contains 1 group.
Thanks for your posting and using Aspose.Cells for Reporting Services.
Please post your report define file here. We will check your issue and update you asap.
The rendering of excel 2007 data only exports data, it does not calculate exact place and set style.
The rendering of excel 2007 needs to calculate all cells' exact place and style.
Please try checking performance settings in Aspose.Cells.ReportingServices.xml file.
<Performance value="ON" IsAutoRowFit ="False" IsMerged="True" IsSetStyle="True" IsConditionalFormatting ="False" LimitCellsNumberForMerged="-1" >
And try the latest version for SSRS 2008(V22.214.171.124).
If you face any issues ,please let us know. We will check it ASAP.