Hi Egor,

To be honest, I always use compression. If you duplicate that romboid 3 or 4 times and save it with compression it will start to slow down to save. I only turned off compression to see what was going on, and that file size will double with each iteration of the drop-shadow (ending up at 3GB per file with my file, but with compression about 11MB but it took far too long to save). But yeah, there's definitely some kind of raster data being saved in the illustrator file.

I’ve also changed the title to better reflect the core problem.
I made a simple test with a 700×500 mm document. I put a rhombus 500×400 mm, set the Raster Effect Resolution to 300 ppi, applied a Drop Shadow (black, 100%, 0, 0, 10 mm), remove all presets (swatches, brushes, symbols, graphics styles) and saved three copies:
1. default one: with PDF compatibility enabled, compression enabled, profile embedded — 11.6 MB
2. one with your settings: no compatibility, no compression, but with a profile — 173 MB
3. and one with compression, but nothing else — 520 KB (K, not M)
If I change the resolution to 72 ppi, the option 3 makes it 127 KB.
If I also hide the object — it’s 121 KB (an empty thumbnail difference).

Sadly I don’t have any insight knowledge on the compression, but why do you disable it? I understand why ignore the PDF-bloatability, but compression...
If you open a file with no compression in a source editor, you should see a ton of mostly-NUL data after the %AI5_BeginRaster line.
So it seems like the raster is being written anyway in the PGF layer of the document, and the effect is not described solely by the parameters... but it seems also the compression is what actually makes it stored like this — or we are just lucky with the compression of the image here.

I agree on the generative mayhem, and the permanent bug-fest, but unless your print workflow demanding uncompressed files, I see no reason to disable the option. Please tell more why you need it disabled.

Paul, I’ve split the report back, since it seems now the main problem is note the tearing...
Sadly, I can’t move the comments back, so here are these quoted:

Hi Egor, the artboard is 700x500mm - though the same thing happens with an artboard much smaller.
I'm not using 'Create PDF Compatible file' at all - I never use that. So the drop-shadow information is effectively a vector in that file. It's obviously a bug as even if I dropped in the dropshadows as image files - I wouldn't get a 450MB uncompressed illustrator file.. Or wait over 30 seconds for it to save.
And my 300dpi exported PDF is less than 15MB, so rasters never need to get as big as 450MB.
Basically I have a relatively simple file with 4 dropshadows in it and each instance is adding around 400MB to the file, making it over 2GB, even if I rasterized the entire file at 300dpi and saved it as an uncompressed TIFF is wouldn't as large as my illustrator file with ONE dropshadow (uncompressed).
Now… compressing it helps, but it's still takes too long to save and is obviously compressing that 3GB down.

Note2: If I set the effects to 72dpi in Document Raster settings, then I get a drastically reduced file - but then that shows that illustrator is not saving this information as vector (what could be simpler than remembering the colour, the offset and size of blur) but somehow rendering these dropshadows as images.
I've included my save settings that I've used since the beginning. I've been using illustrator since 1989 so I'm pretty au fai with the software and its bugs. But the fact that this happens in the last four iterations of illustrator along with the broken shadows is pretty annoying. I do wish bugs were given as much attention as whatever new generative AI bloat we get added to justify the subscription. But here we are.
Thanks for the response.

The issue with the broken shadow is known.
The size though is a direct consequence of the way these effects work — they are raster-based, and are computed using the resolution you set up in Effect > Document Raster Effects Settings dialog. In most cases the parameter should not exceed the resolution you are going to use to export your final image.
When you save a file with the 'Create PDF Compatible File' option checked (and it’s enabled by default and is not sticky — requested here: http://illustrator.uservoice.com/forums/333657/suggestions/36926863), the full copy of the resulting raster gets saved into your document. So the larger the shape, the higher the effect resolution set, — the heavier is a file.

Paul, the attached file got lost, it seems. Is it a simple .ai file?
If it fails to get attached once again, please tell the size of the artboard.