Failure to install Windows 10 April Update(version 1803)

Strange. Well there is only one post at the moment so maybe this works

I did finally get my system to update successfully. It took a mixture of time, persistence, diagnostic effort, and luck. I'll skip the red herrings and false starts and get right to what worked.

The essential information about my system is that it uses an ASUS X99-E motherboard with a RAID1 disk array (two mirrored drives).

1. I used the media creation tool to burn a DVD of Windows 10 1803.
2. I wiped my disk array clean.
3. I booted from the DVD and tried to install Windows onto my empty disk array.
4. When that failed, it was pretty clear that there was some fundamental conflict. Having previously stripped the system down to mouse, keyboard, and internal drives, there wasn't much left.
5. I deleted the RAID and left it as two separate drives.
6. I booted from the DVD and successfully installed Windows 10 1803 onto one of the two empty drives. That worked!
7. I rebuilt the disk array.
8. I booted from the DVD and successfully installed Windows 10 1803 onto the empty array. That worked!
9. That proved Windows 10 1803 is not fundamentally incompatible with my (Intel IRST) RAID controller chipset, but was for some reason incompatible with the array I'd started with.
10. I restored my working system onto the array that was now working with Windows 10 1803. That wiped out the update, of course, but I had a running system with all of my apps, files, and settings.
11. I ran the 1803 update again.
12. The update worked.
13. I now had a working 1803 installed on a RAID1 array.
14. I did have to fetch and install a new version of the IRST management software, but that was it.

I don't know how useful this is for you. I have no clue what was different about my disk array after I destroyed and rebuilt it. And I'm sure most of you don't have a similar setup. If you do, then give this a try.

Clearly, this entire update is sensitive in the extreme. I have another, much simpler, system that is also giving me fits. Nothing I described here will help with that. There must be something entirely different going on.

I see a title page there. But no substance or way to get to a blog from there;

Finally got mine updated today after about 20 failures at 86% with Error Code: 0xC1900101-0x4001E. 

I wrote a blog about it as it's a bit complicated. I hope that helps some of you. 

https://jukkakohtala.blogspot.com/2018/08/windows-1709-upgrade-to-windows-1803.html

I forgot to ask is this update necessary? Or can we tell it not to download and install it?

Microsoft used to stop the security updates for older versions/builds of OS (W10 as well). So I suppose all important updates should be installed because of security of my PC.