Partitioning: What? Why? When? and How?

windsor_richard

windsor_richard

Lekker
Ok...
I'm currently running a post because my powerbook isn't very happy, but while i'm posting that i'd like to know a little more about partitioning.

What do you do?
Why do you do it?
When would it be helpful?
How is it done?

Thanks guys.
Rich
 
You would partition a drive when you initially set it up using Disk Utility.
Some people do it to keep apps on one partition, system on another, swap, etc.
Run two different systems on separate partitions.

Not really helpful or needed in OS X, but it's a matter of personal preference.

I replied to your other post about the hard drive problems you're having.

If you're thinking partition would help incase something like that happens, it could possibly help in some situations where the main system was screwed up, you could boot into a system installed on a different partition.

But, if a drive goes bad, having a partition with another system to boot from wouldn't help.
 
I'm splitting my HardDisks up into at least 4 partitions:
- swap
- Mac OS X
- Other Programs
- Users

swap:
This is to keep the swap from filling up the Mac OS X partition and awoiding fragmentation of the individual swap files. Also useful for Photoshop, Gimp, Graphic Converter swap files as well as other programs that like to have that kind of temporary files you don't want to have floating around all over the place.

Mac OS X:
This makes it possible for me to do a completely clean install without ruining anything else I've installed. Only the programs that absolutlely insist on being installed on the boot partition are installed here along with the Apple programs

Other Programs:
Keeps them away from the Applications folder so that I don't have to re-install after a clean install of Mac OS X

Users:
Keeps the home directories away from the Mac OS X partition so I can wipe the Mac OS X partition without fear of loosing my user data.

Disadvantage: You might run out of space on one partition while still having lots of space on another partition. iPartition (or similiar) can help in that situation if necessary.
 
As to a drive going bad, usually it's just a single partition that's gotten it's data corrupted in some way. In that case having separate partitions really helps.

On the other hand, if the whole drive dies, there's not much one can do except sending the whole drive to a resque service. And even in that case having separate partitions might be helpful depending on the kind of damage done to the drive.
 
Most people consider partitions to be more trouble than they're worth. For any people they probably are. I find them essential, though.

windsor_richard said:
What do you do?
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I have two partitions, both 20GB, one that's about 17GB and one that's about 20GB. My 17GB partition is my boot partition; it holds my system, my applications, and my Home folder (which contains most of my personal files and projects). The 20GB partition holds downloads, music, movies, and just about everything that is not A) part of my system or B) an application, or C) my own personal creation.

I also have a 720GB disk image on my main partition, which I use as temporary swap volume for things like playing videos and mastering CDs. It's effectively a third partition, although for some reason it is slightly fragmented (I don't know why, since I created it on a completely fresh volume that probably had 5-10GB of contiguous free space). Next time I repartition I'll make it a real one.

Why do you do it?
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There are two main reasons I use partitions:

1. Performance. Despite what many people will say, fragmentation is definitely an issue on OS X. For this reason, I try to keep activity on my boot partition to a reasonable minimum (I say "reasonable" because if I went to the effort I could move virtually everything but the system to a different partition — but there are diminishing returns, so I'm not going to be a fanatic about it). By moving things like movies and downloads, which are likely to be deleted or altered often, off my boot partition, I help reduce fragmentation of my system (most importantly the invisible virtual memory swap files).

Using multiple, relatively small partitions also makes "hardcore" optimization easier, because I can more easily dump the entire contents of a partition to a backup, and then reinitialize only that partition. This is the safest (albeit not the most effective) way to perform disk defragmentation. I do this semi-frequently with my non-system partition; I dump it to my 30GB external drive, reinitialize it, and then dump all the data back.

My swap volume is used mostly for video, because it's very important that it not be fragmented. Both my main partitions are just too heavily fragmented for heavy-duty video playback.


2. Error isolation. Over the many years I've used computers, I've had many software problems that rendered one or more volumes unreadable/corrupt. In many cases these problems only effect one mounted volume, not an entire disk, so using multiple partitions will protect some of your data and make recovery easier. But like bobw said, hardware problems are a whole other ball of wax, and there's nothing you can do about them (except having good backups).

Using my second partition also helps ensure that I keep a good amount of free space on my boot volume. OS X likes to have several GB of free space for things like virtual memory. If it fills up....bad things happen. With my setup I won't absent-midedly fill it too much. And it also prevents things like buggy video encoders from stuffing my boot partition to the gills by bloating its output file to 10GB for no good reason (which has happened to me so....many....times....GAAAAH!).

When would it be helpful?
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When any of my reasons above apply to you. :) If you deal with video a lot, you'll probably want a separate partition for performance.

It's also useful for maintaining multiple OS installations. Most people even recommend putting Classic on another partition even though you don't need to, for performance reasons. Back when I dual-booted with OS 9, I had a third partition for it. I considered that very important for both performance and error isolation.

If you're on Tiger, you might want to have at least one partition that Spotlight doesn't index. It can be a performance killer when you're performing operations on many files in succession. And it makes my disk much noisier than I like it to be. :)

How is it done?
Click to expand...
In Disk Utility. You can only create partitions when you initialize a disk, which of course deletes all data on the disk. So it's probably too much trouble, IMO, but keep it in mind next time you have an empty disk to work with.
 
Just to chime in: I don't partition single drives; rather, I use separate disk drives. It's like getting all the benefits of partitioning without having to partition. Plus, if I want to add another partition, I don't have to back up everything on the disk, reformat and repartition it, then restore the data -- I simply add another drive to the mix.

For casual home use of the computer, partitions would probably be more headache than they would be beneficial. For a power user/tinkerer, though, they're essential.
 
"Simply" in your way, ElDiablo, means "money", though. ;) But I agree that partitioning for most users is too much hassle for the benefits.

Side question: How do you force Mac OS X to use another partition for swap?
 
Okay. I've read some things about this on macosxhints.com and followed some links from there. It seems that there is not one simple way to do it - and any solution can (and sometimes will) break with a "simple" software update from Apple.

I guess I'll only do this when Apple adds an option to the system setup.
 
Gotcha,
I never fail to be bowled over by the knowlegde and advice offered on this site. Everyone is incredibly helpful.

I think bearing in mind what people have said, when i fix my beautiful powerbook, i'll steer clear of partitions.

I have 60GB on board (although it's currently knakkard long before it should be), and 100GB exHD. I don't deal with a lot of video, i'm a fairly simple graphic design user. In the future i'll keep things organised accross my on board/ ex memory.

Thanks again.
 
i've ressurected this thread, as it's completely suitable for what i want to do.

I'm a tinkerer. this means that my computer always goes down at some point, because i tinker with stuff i shouldn't. conditioning doesn't really work in my case, so i need the possiblity of wiping the system partition and starting again.

i have 2 250gb internal hard drives, a music folder that is currently 112mb, and will expand, so that can be given a whole disk to itself. photos can also go on here.

i want the other drive to be 15gb system, 15gb applications, and the rest my home folder. what do i need to take into account to make sure i don't run into problems? i heard once that you need to drop the libraries back into the new install to make all the links work again, for example, flash acts up funny if its been moved.

is there any documentation around for moving the home folder off the sytem partition, and also the applications folder?

any help will be appreciated, obviously.
 
You could try this.

Use SuperDuper to clone your User folder to where you want it.

Go into Netinfo Manager in Applications > Utilities. Select users, your user name, and change the Home line to whatever path you want.

You should do this as Root.
 
yeah i've just been googling and come to the same conlcusion. the real clincher though is the applications folder. i want to keep that seperate from the OSX partiition, that's the one that takes the longest to get back.

how can i have the applications folder on a seperate partition, and have everything work ok?
 
Partitioning just seems to rob your system partition of valuable virtual memory space for when you're doing intense, high RAM hogging work. And, the system drive works better anyway when it's as free of files as possible.

That's why I store my files on an external firewire drive and do regular cd back ups. Seems to work well.

The great thing about computers, though, is we can do so many great things with them. We're up to our own devices, so to speak. :)
 
Moving the applications should be easy, since that's not a low-level system thing. Move 'em to another partition, drop in a symbolic link at the original location, and you should be good to go.

Or you could just move your non-Apple apps to another partition, and you won't even need to bother with symlinks. Only Apple's apps are stupid enough so that they'll screw up if not in their default locations (go figure).

I've been interested in doing this kind of partitioning to keep a separate VM volume, but I've decided against it because it makes every update potentially risky. I remember that when Tiger came out, the methods people used in Panther no longer worked. I don't want to risk that happening when I upgrade to Leopard.
 
symbollic links? like aliases?

i had another idea. have two partitions, one with just os x on, and another with osx and all your applications installed to. keep the one with applications attached clean, don't use it. then, use the one without apps as your day to day build, with all your apps in the dock etc being from the build with the apps. this way, the everyday os can be wiped when ever you want, and the apps still have their proper libraries. i'm going to try this i think.
 
Since you'll want a backup _anyway_: Get an external backup drive. 300 GB or more. Then you can keep system and apps on the main drive and only use the other 250 GB drive for your music and photos.

I just wouldn't go the route of having a "small" system volume. It's a call for trouble. You want as *MUCH* free space on the system volume as you can get.
 
ok here's an update of what i've got.

10gb - main system os, day to day, but other than that, no changes to the install, no languages or additional anything. 6.7gb free (i.e more than 15 percent)

20gb - other system, all applications to be installed here, and all the apps in the dock point to the applications folder on this partition. all seems to be working fine. iDVD templates are all present, garageband loops as well. (edit: update: although mail etc works fine from the new location, the system can't see that as default. eg clicking a mailto link in safari causes the mail in the system volume to launch instead)

186gb - home partition. one folder, which is the home folder backup, which i've blessed using netInfo mananger to be the systems home folder. funnily enough, this means that all my previous user settings were maintained. saved a lot of work thruogh this.

20gb - empty as yet. may in future combine with 10gb system partition to create a system volume with 26gb free, for VM. see how the 10gb works with 6gb free for now though.

and all my music on a seperate harddrive.

hopefully, this should work out to be a system that i can erase and install OSX really quite simply.
 
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