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In Depth Information
The following sections provide background on what contributes to the ECS process size, as well as what
can contribute to the CPU usage. Understanding the ECS architecture discussed in Chapter 3 will help
you apply the concepts discussed here.
ECS Process Size
Excel Services was designed to cache workbooks and other objects in memory to improve performance.
The ECS process size can (and most likely will) become one of the larger (if not the largest) process
executing on the application server. Consequently, the process becomes a focal point during capacity
planning and performance discussions.
Excel Services loads workbooks that are saved in either the .xlsx (Excel Workbook) or the .xlsb (Excel
Binary Workbook) file format. The Excel Workbook file format is the Excel 2007 default, and is an
XML-based file format. As the name implies, the Excel Binary Workbook file format is a binary format.
Workbooks saved by previous releases of the Excel client are not loaded by Excel Services.
The workbooks saved in either of the two supported file formats have a disk size that is significantly
different when compared to the Excel 11 file disk size for the same workbook. Both the Excel Workbook
and the Excel Binary Workbook file formats typically consume less disk space than the same file saved
in an Excel 11 file format. The size difference depends on the workbook characteristics.
The following table provides a comparison of three workbooks and their file size on disk. The primary
difference between the workbooks is the used range for each: A1:J5000, A1:AD8500, and A1:AN12500. Each
workbook consists of numbers populated in each cell in the used range with no cell containing more than
11 characters. Ten percent of the cells contain formulas and 70 percent of the cells contain number
formatting or cell formatting. These workbooks are a simple example, and every workbook that is compared in
this manner will show different ratios between the two file formats, depending on the contents and
characteristics of the workbooks.
.xlsb Size (Bytes)
.xlsx Size (Bytes)
Each workbook loaded by Excel Services is written to the ECS local workbook disk cache for the ECS
loading the workbook. If the workbook disk cache feature is disabled, then the workbook is removed from the
workbook disk cache when the associated sessions are closed. You can configure the size of the workbook
disk cache through the Excel Services administration page, which is covered in Chapter 7. The amount
of disk space consumed by each workbook written to the workbook disk cache depends on the workbook’s
contents and characteristics. However, there is nearly a 1:1 ratio of the workbook’s size when it is saved to
disk and when it is saved to the workbook disk cache.