How best to set up a separate /home partition, and pros/cons

[Liam Proven]

On 27 November 2012 11:22, Kaj Haulrich <kaj.haulrich at adslhome.dk> wrote:
> On 11/27/2012 10:42 AM, Liam Proven wrote:
>
> <quote>
>
>> You can only have 4 primaries per drive, total. The extended partition
>> /is/  one of those primaries, leaving you just 3 to play with. They are
>> a precious and very limited resource - do not squander them.
>
> <unquote>
>
> That's true only insofar the 'old' BIOS is concerned. I guess most PC's
> nowadays come with EFI firmware (or UEFI) on the motherboards. So if you
> have one of these  and choose to boot from an EFI-partition (FAT32) you can
> have an unlimited (well, in practice) number of primary partitions.

There's more to it than just the firmware. You also need to change the
disk partitioning format.

The "traditional" PC format is (informally) named "Master Boot Record"
after the name of the structures in the first block of the disk. This
is what imposes the 4-primaries restriction.

EFI also allows the newer GUID Partition Table (GPT) partitioning
system, also used by Intel Macs.

Windows 2000 through to Windows 7 also supports "Dynamic disks",
another alternative again. Windows Server 2012 and Windows 8 support a
newer replacement called "Storage Spaces". Oracle Solaris has ZFS with
its own scheme; the BSDs all have their own systems of "slices" within
their own dedicated primary partitions. Running Mac OS X on a
Hackintosh - or using Mac disks - opens up the possibility of Apple
Partition Map (APM) disks. Then there is the Sun workstation format.

So as soon as you step outside the plain old DOS system, it gets
/much/ more complicated. It is /not/ simply about firmware.

As such, I am sticking with the simplest and far and away most common
system, the default one and the only one that x86 PC-compatible users
are most likely to encounter on disks below 2TiB: MBR.

It is /not/ safe to say that PCs with EFI allow more than 4
partitions, any more than it's safe to say that motorcycles have 2
wheels and cars have 4. I own two motorcycles; both have 3 wheels.
There are also 3-wheeled cars, 4-wheeled motorcycles, 6-wheeled cars
and so on. Indeed whether it's a car or a motorcycle doesn't actually
have much bearing on how many wheels it's got.

Whether a PC has EFI or a BIOS doesn't actually have much bearing on
whether it allows 4 partitions or 42 of them. That's a question of
MBR, GPT or something else; the only link is that only an EFI PC can
boot off a GPT disk. (Although I bet not all of them can.) And you
might encounter non-bootable GPT disks on non-EFI PCs.

So be very careful of generalisations. They can be dangerous.

The only ones I'd tentatively offer on this subject are these:

* If a disk is more than 2TiB in size, it's probably partitioned with
GPT; then, the 4-partition rule no longer applies.
* If your PC has an old-fashioned BIOS and not EFI, then it probably
can't boot off a >=2TiB drive.

Even those are not nice and clean and clear-cut.

-- 
Liam Proven • Profile: http://lproven.livejournal.com/profile
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