No. I mean you should not leave any unpartitioned space, you can do that if you want, but you can use all the available space.
No, I mean you need not put the free space in a partition, you can leave it unpartitioned (and that would be even better if you want to resize the others) Also you may want to have that unpartioned part in between the partitions (and not at the end).

I wouldn't say triple, but WinSxS is part of the problem.

https://msdn.microsoft.com/en-us/library/aa376307.aspx

http://blogs.msdn.com/b/e7/archive/2...isk-space.aspx

Right now I'm looking at my very-much-used laptop and it's C:\Windows is just 21 GB, but the Users (just 1) is at 52GB (a lot of that will probably be managed better on new desktop). Do you think 80GB is good for a Windows Partition or no? And any idea why my Users is so High?

users have their own files, so you need to check. There can be documents, videos, whatever...

OK but does that mean 80GB should be enough for a Windows 10 Partition or no?

for the os itself that should be enough

OSX: Uses quite a bit of space for some reason. The minimum listed is 8gb but that's pretty unbelievable and probably wont even allow you to install. The minimum working I would say is closer to 35 40gb.
Windows 10: Like other posters here I would recommend around 60 to 80gb for windows (Updates tend to eat alot of space along with other MS buffers and fluff) 60 is actually what I use at work for workstation VM's (win 7).
Linux: Probably the leanest ( even with Ubuntu ). Root parttion on this can be pretty small. 6 - 15gb is fine. Other distros can even be smaller.

Is 30 enough for OSX you think? Yosemite is about 15GB on a fresh install.
Is 80GB enough for my Windows partition?
And is 30GB overkill for my Linux partition; if so where should I put that space instead (Windows, Mac, or Storage)


4) My 3TB will probably solely be NTFS; does this mean all my linux programs will have to fit in to that Linux partition?

NTFS is an MSWin format, so although Linux has tools to read/write data files on there, I definitely wouldn't put any Linux SW on there.
I also wouldn't put any Linux DB on there either eg MySQL, Postgres...

When thinking about disk space here, you need to distinguish between programs (inc cfg files) and any data files you may create.
We can only advise on the former; after that its up to you.

FWIW, exvor's numbers for Linux SW sound about right to me - it does rather depend on what SW you install, but 6-15 GB is about right imho.

By SW you meant software correct? and if so do you mean 6-15 GB solely for the software, excluding the operating system or 15 total including the OS too.

6 - 15 GB for OS and most app SW (yes - software).
Just the OS might fit in 6GB - it really does depend on what you install, that's why we can't give exact numbers.

Bearing in mind that I've already said I'm not a multi-boot proponent. Here are a few additional thoughts:

1. As chrism states, for Linux it really depends what you install. I install what I feel to be a fully inclusive Linux distribution, Debian, or Ubuntu, onto single purpose boards, but I do not tune things down much for size; rather instead disable services from running. I usually use 8 GB SD flash cards for this. Typically I end up with less than 40% disk in use when I start paying attention to anything storage related. Therefore this usually fits within 4 GB in my opinion. I've also booted many virtual machines and you allocate space for them on your existing hard disk. I usually pick either 8GB or 16GB and never have had any problems at all. So I do feel that 16GB is more than sufficient, even to allow for installing extra stuff. I feel you'll have available extra space.
2. Linux, OS X, Windows. Each of them has a "concept" of the person's home. Hidden files and directories which pertain to the user's application settings, their data files, and their download files, are natively placed within this directory. You will want to practice regularly defeating this concept, or telling each operating system that your user "home" is on that 3 TB drive instead of on the SDD.
3. Management of the 3TB drive concerns me somewhat and also the purpose, or not of marrying these systems - To me Linux can see FAT32 and so can Windows. No idea about OS X. I do know that certain files, like MS Office files, will be translated in a minor way by the Linux Office tools, enough so that people using regular MS Office will be like "What'd you do to that document?!?" Further, Windows will translate text and code source files from Unix format to DOS format and that will annoy you if you have that problem. It stands to definitely screw up scripts and Makefiles. So I wonder how much of all the data you intend to share between the three systems.
4. My thinking is that the person multi-booting is doing so, so that they can run programs on one system type which they really can't on another, or are far too difficult to run on the other. And since you're going to multi-boot and maybe have MS Office documents, you'd then do that in the best place for you, whichever OS and tools work best and don't cause people you interact with to have trouble reading documents you send to them. So what do you do with that 3 TB? You should have a native "home" partition for each OS. Can you just use a universal format so that all OS's can access it and then truly shared data is accessible by all? What size or sizes would you then choose?
5. And OK I'll attack Windows a bit. Because they try to abstract so, so much. Whatever everyone else is saying, I agree. I don't think I've seen anyone say anything less than like 30 GB, if not much higher. I would tend to go higher. I fully agree that more would be better with Windows, not because it will be so much nicer, but because it will want and take and if/when it runs out, it will not behave pleasantly.
6. Final other thought is that the tendency these days to "upgrade" is reaching a common concept. I do have OS X and Windows, both Windows 10 and OS X Version 9(something) took like 6+ GB in disk for their downloads! On one hand, makes good sense, "get it all down, verify it, then reboot and perform the upgrade", but .... WOW!!! That's a LOT of size, lengthy download, and just very big. So downloading large chunks like that and storing them, then using them post next boot is a consideration. I'd definitely make sure that external HD is USB 3.0 and can't imagine that it is not. But also that the computer itself has USB 3.0 to talk to that drive.

@a: is a 30GB partition overkill then? Should I just make the partition 20GB? (20, or 25?)
@b/d: How do I do this?
@c: When you save a .docx in libreoffice, it should be the same, regardless of operating system. I don't know what weird processing thing you're referring to but that sounds awfully odd.. I save .docx's all the time on OSX and bring them up on Windows just fine. D:
@e: I agree they abstract that size, a lot. I'm planning on making my Windows partition 80GB.
@f: the 3TB hard drive is actually an internal one. 7200 RPM, 64MB cache

30 GB is not overkill. My personal top number would be 16G. It's not worth worrying over 14G of difference.

People edit docs in MSOffice. If I edit them in my Linux form of office, I forget if it's OpenOffice or LibreOffice, it screws up images, tables, and formatting. I don't invest much time in diagnosing I just use the Windows system.

For Linux use the usermod command.

Okay, thank you!

^^