Partitioning: What? Why? When? and How?

[windsor_richard]

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

[bobw]

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.

[BjarneDM]

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.

[Lt Major Burns]

how do you set up the users on another disk? i thought they had to be on the boot disk

[BjarneDM]

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.

[BjarneDM]

Moving users:
Modifying the home directory in 'Netinfo Manager' along with some work in Terminal.

[Mikuro]

Most people consider partitions to be more trouble than they're worth. For any people they probably are. I find them essential, though.

Originally Posted by windsor_richard

What do you do?

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?

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?

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?

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.

[ElDiabloConCaca]

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.