dual ( 7 / 10 ) boot question

i'm building a new windows 10 desktop to replace current windows 7 desktop but since all my software is only guaranteed to run on 7 i plan to build the new desktop as a dual boot ( 10 + 7 ) first and then eventually ( in a year or two ) convert to 10 only.

i haven't purchased any parts yet but i will be using intel X299 platform, tentatively Asrock X299 taichi motherboard and either 2 or 3 Samsung 960 Evo M.2 SSDs 250 GB each in RAID 0.

so the plan is set up the raid with total 500 GB and create a 100 GB partition for each windows with 300 GB unallocated space. the unallocated space will allow me to expand either partition as needed in the future. then eventually i will remove the windows 7 and its partition.

the question is what would be right way to do that - should i install windows 10 first or windows 7 first ? ( to make sure the 10 continues working once 7 is removed )

if removing windows 7 partition is too dangerous i would have to go with 3 X 250 GB SSDs and a total of 750 GB space in which case i would never need the extra space freed from windows 7 and i could leave both OSs forever but it would be a waste of extra $150.

i hope the question is clear, if not - let me know.

Always install the oldest OS first, if you can, when setting up dual booting. So that would be Windows 7 first. Installing the newest OS last will update the boot files to their latest version. Installing the older OS last will downgrade the boot files to a previous version - you may still get dual booting with an older menu style - or it may break booting the newer OS altogether.

NavyLCDR said:

Always install the oldest OS first, if you can, when setting up dual booting. So that would be Windows 7 first. Installing the newest OS last will update the boot files to their latest version. Installing the older OS last will downgrade the boot files to a previous version - you may still get dual booting with an older menu style - or it may break booting the newer OS altogether.

thanks. i read that you should generally install older system first when doing dual boot but then i came across a thread ( don't remember where ) where a guy had two operating systems on two separate hard drives and when he simply unplugged one hard drive the other wouldn't boot because some sort of boot partition was on the drive he unplugged even though the system he wanted to boot was on the other drive that was still plugged in. his problem stemmed from him unplugging the drive where the FIRST operating system went which also received the boot partition, which got me worried about installing first the system that i want to eventually delete ...

however in my case i won't be unplugging anything and both OSs will be on the same RAID so obviously different situation ...

so are you saying it doesn't matter which of the two OSs i plan to eventually keep ? i should still install the older one first ?

EDIT: as i mentioned previously if there is no safe way to remove one OS and reclaim the disk space without risking ruining the other then i have the option of keeping both forever - i would just need to start off with a bigger raid because on my current system i just ran out of 256 GB SSD drive C ( with all storage on separate rotational drive D ) so for the next build i want to have available 500 GB for windows 10 plus 250 GB for windows 7 or 500 GB for both IF i will eventually be reclaiming the space used by the 7. these will be only for OS / program files. i will move the rotational drive D with all my files from old desktop to new without touching anything on it.

g1981c said:

so are you saying it doesn't matter which of the two OSs i plan to eventually keep ? i should still install the older one first ?

Make sure you are installing SP1 Windows 7 64-bit. That is the only version of Windows 7 that will install in UEFI mode. Windows 7 and Windows 10 both, by default, create a separate partition containing the boot files. In legacy BIOS the boot partition is called a System Reserved partition. In UEFI, the boot partition is called the EFI System Partition. When you are installing Windows, it will look for an existing System Reserved or EFI System partition that the computer is normally booting from. If it finds one, then it adds the Windows being installed to the existing partition - it will not create a new one. That is why when a person installs a second version of Windows onto a second drive, it will stop booting if they later remove the first drive. The second Windows did not create any new partitions for booting - it only added the second Windows to the already existing boot partition on the first drive.

In your case, you will be installing the second Windows into a separate partition on the same drive. If you remove either Windows installation by removing or reformatting it's partition, the boot partition will still be on the drive and you will continue to have boot capability. The only thing you will be "breaking" is the pointer in those boot files to the Windows that you delete. It's only when you remove the System Reserved or EFI System Partition that you damage booting - such as reformatting the entire physical hard drive/SSD or removing it from the computer.

CountMike said:

I would strongly suggest separate SDD for one of Windows. M2 RAID0 + dual BOOT on it is just asking for trouble.

The problem with this is when I uninstall windows 7 the space will be wasted as I won't be able to add it to the raid with windows 10 on it.

Anybody else think my plan is asking for trouble ? My win 7 is on SSD raid right now - two 128GB sata SSDs.

AddRAM said:

There is no reason to use raid with ssd`s.

Why don't you just install 10 and see if the software you need will run on it.

I watched a video where they specifically tested the raid I have in mind - 3 x m.2 SSDs and they said it was worth it ...

As for why not try windows 10 first ... It seems stressful. I want to get everything over with in a few hours and get on with life.

CountMike said:

Why not W10 first ? Because second OS will "take over" BOOT sector and UEFI and you would want W10 to handle that.
I don't know why you want them in RAID 0, any error on any disk in that RAID will break everything. both of your OSs too. SSDs are fast enough as singles and RAID can bring you only some bragging rights without much of real world increased performance. It's also slower to BOOT because of raid drivers and BIOS have to set it every time.
As for "couple of hours for setup" forget it, if you are not really proficient with RAID, it's gonna be more like couple (or more) days.

But it's free - you think I can resist that ?