[CentOS] SSD as system drive - partitioning question

[Les Mikesell]

On Wed, Apr 18, 2012 at 2:05 AM, Frank Cox <theatre at melvilletheatre.com> wrote:
>
>> You want to create two partitions on the SSD and three on the HD. The SSD
>> partitions should have the mount points /boot and /, while the HD partitions
>> should have mount points /tmp, /var and /home. That's all there is to it,
>> really.
>>
>> It seems that you are just missing the observation that (by default)
>> everything that does not have its own mount point will be put as a directory
>> into / during the installation. However, directories that *do* have their own
>> mount points will be put on their respective drives, and just logically
>> "mounted" into the / tree. So you just create separate partitions for stuff
>> you want to go to the HD, and everything else will go inside the / partition,
>> which should be on the SSD.
>
> Aha!  The light just came on for me here.  Thanks to everyone for your
> observations and insight on this; I now have a better understanding of drive
> partitioning than I did before.

The original unix layout split /bin, /lib and /usr/bin, /usr/lib  with
the intent that everything you need to boot and mount other partitions
had to be in /bin and /lib on the root partition which might be tiny.
After years of big, cheap media availability things have gotten sloppy
but booting from an ssd puts it back in perspective.

> I just now started  formatting this new machine.
>
>> Btw, I stopped bothering to create a separate /boot partition some time ago,
>> and never looked back... What is your usecase for having it separated from / ?
>
> Nothing, other than that's how the default partition scheme seems to work on my
> other Centos installations so I figured if that's the default there must be a
> good reason for it.

Eons ago, PC bios didn't know how to boot data beyond cylinder 1024 -
long after disks were bigger than that.  So the safest approach was to
make a small /boot partition as the first thing on the disk.  It still
works and has no harmful side effects as long as it has enough space
to hold future kernels and initrds.  It also lets you use LVM and
filesystems that grub doesn't understand for your root filesystem.

-- 
   Les Mikesell
     lesmikesell at gmail.com