Monday, August 30, 2010

File Size - A Red Herring?

Every now and then I read a post on a blog or user forum advocating various techniques to reduce a Revit project's file size. Is file size alone a serious concern or measure of a successful project? I've heard of people insisting on a maximum file size allowable for a model.

I think File Size is a red herring.

Sure a large file will require more memory to open and this will affect performance. The biggest annoyance will be the time it takes to open the file. Linking a large file will affect the host too. File size is a worthy consideration but there are many others that often get ignored.
  • Warnings - These get ignored for ages and pile up. Some of these are more offensive than others. For my money anything that involves calculations is a worry. Room, space and area errors caused by boundary issues or redundancy is wasting your cpu's time (and yours), even though it is really fast. The truth is that any warning is a waste of "space" and "resources" to some degree.
  • View Detail - Do you have a lot of views that are using fine or medium detail level but have scales like 1/16", 1/8"=1'-0" (1:200, 1:100, 1:50)? These views won't really show this level of detail for all elements effectively and you are asking the computer to show it anyway.
  • Huge Sketch based elements - A toposurface with huge numbers of points or floor sketches or filled regions with very large numbers of segments will hurt performance. Same for area plans and their boundaries. These features are meant to be used with the fewest number of segments to create a representation of information. I've seen filled regions used to completely document a color scheme or floor pattern concept that account for thousands of line segments instead of a simpler actual color scheme applied based on information...instead of drafting because it is familiar.
  • Unused Content - Families that are not going to be used at all can contribute to some bloat. Especially if they are complex families that are quite large to begin with. Check the stock content, rarely if ever are they over 200 kb. If they are they probably have an array or some other complexity.
  • Content Complexity - Families that are over-modeled or at the very least are not using Detail Level and Visibility options effectively. Families that have a large number of formulas or using arrays are another.
  • Hosts overloaded - Autodesk has indicated in the past that they've determined that large walls with many many hosted elements can hurt performance. They recommend using multiple walls by floor(s) or stacked walls to minimize this.
That's just a few items, this post would get a bit too long to dig more, perhaps another post. What about the file sized focused techniques to reduce the file size itself?
  • Save As - It's often mentioned to use Save As to make a new central file. Sure, the result is a smaller file, but why? We just started over, no save history, no user log files and no backups. Yes we've stripped out elderly data that may not be necessary now but guess what? As soon as the crew gets back to work watch how quickly the file becomes roughly the original size.
  • Compact Central - An oversimplification, it is akin to the operating system performing defragmentation of your computer's hard drive. I prefer to think of it as asking Revit to clean up after a busy day. It allows Revit to reduce file size but I think you'll find that it isn't as shocking as using Save As. Shouldn't be too surprising though since we aren't getting getting rid of save and user history.
In my opinion we shouldn't just focus on file size. It's one of many things to consider, a symptom perhaps, not a disease itself. One piece of wisdom I can share that Scott Brown (a friend in Orlando working with The Beck Group) has offered in the past is this:

File Size @ SD x 3 = File size @ CD
SD= End of Schematic Design
CD= End of Construction Documentation

I can confirm his general observation based on my experience. Something to consider.


ambrozote said...

Hello Steve,

I am wondering, is there somewhere in revit a place where I can get the entire Warning list?
I mean, every warning revit is capable to pick up from the model?


Steve said...

Sorry, I am not aware of the "factory" ever publishing a list of all the warnings they've created in order to respond to issues.