This screen controls two important aspects of exported layers.
Trim VHD Upon Saving
VHD will be automatically extended to a required size once more resources are added to it. However, when doing a clean-up by removing bulk of files and/or registries, there is usually free space left which is not automatically trimmed. As such, VHDs tend to keep their sizes, even though a lot of package content may be already removed. Trimming ensures that the VHD is scaled down to actually benefit from reclaimed space.
Trimming can be disabled by selecting the Never option.
In order to enable trimming, select one of two options:
•Automatic - ensures that the VHD is trimmed if a certain threshold is reached.
•Always - VHD is always trimmed with every save operation.
Trimming can be considered a costly operation which may take some time. Therefore the automatic trimming ensures, that it is only executed if the gains outperform eventual performance penalty. The automatic trimming uses the following conditions and thresholds:
•The size is optimized if the package is considered "big" (more than ca. 77 MB), or...
•The trimming would result in the output disk be at least 10% smaller in size than before the operation.
This means, that the automatic routine will never trim small packages (less than ca. 77 MB) or the ones, that would not otherwise benefit much from the trimming.
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Note: PackLayering arranges around 30% free space to be reserved. The numbers and estimates above consider the total size of the package without this extra margin. |
