I have a mid 2011 iMac that boots from the HDD. I am wanting to upgrade, but I was wondering how High Sierra performed on spinning disks. Does anyone have any experience? Also, does anyone have any experience with converting a boot HDD to APFS. If so how was the performance? I know Apple doesn’t automatically convert. The only reason I can see not to is performance. But what about APFS would make it less performant on a HDD?