Indigo renders in strange intervals

[Headroom]

Ive not worked with indigo for a good while ad recently updated the Blender based toolchain with the latest and greatest.
Indigo 3.8.26 renders in short bursts on almost 100% CPU utilization and then takes regular brakes. Where the time ticks but the samples per seconds does not progress> All still on my almost 4 year old iMac now on Yosemite 10.10.2.
That has not happened before!

[OnoSendai]

Indigo may be saving a very hi res image to disk. Try turning off IGI saving in the options dialog.

[Headroom]

That did the trick. I turned it off and now the intervals are gone. Thanks for the tip!

The image resolution I am rendering is only 2550 x 1940 with supersampling set to 3. Its not different from what I've done with prior Indigo versions.
Now that I think about it, does the number of light layers (17) increase the size of the IGI ?

[Oscar J]

From my experience it does, pretty dramatically.

[Silmä]

the way I noticed it maybe a couple of years ago (when I was using a computer with very limited memory), each light layer was basically it's own full-resolution uncompressed 32bit bitmap.

That is, HUGE

I don't know if that has changed since.

[CTZn]

I don't know if that has changed since.

I don't believe this has changed, and I'm not sure allocating resources into compressing a huge IGI file would show any benefice on a given node.