[Gllug] To partition or not to partition

[Nix]

On 11 Oct 2010, Bruce Richardson spake thusly:

> On Mon, Oct 11, 2010 at 01:19:56PM +0100, - Tethys wrote:
>> which I'm playing around at any given time). These days, I can't
>> understand why anyone would do anything other than /boot + LVM.
>
> For my personal systems, I do / on the first partition and everything
> else on LVM.

For my personal systems, I do *everything* in LVM-atop-RAID, including
/boot, and use an initramfs to bring it up, bring up the RAID array, and
so on. I can't live without the resizing flexibility of LVM, and I won't
live without the ability to survive disk failures. I've had enough of
depending on a single spinning plate of rust.

>               I don't mind sacrificing a few gig to the first partition
> for one less layer of VFS on the most crucial partition.

Pretty irrelevant, really, as LVM only interposes *anything* in the
block I/O path, and that only happens if you're hitting the disk, which
is much slower than a tiny bit of extra computation could ever be. The
stuff which is heavily used (e.g /lib and /bin) is in the page cache all
the time anyway, and page cache accesses don't go through LVM at all
(well, reads don't: writes obviously do when they get flushed, because
that hits the block I/O path again).

>                                                           But then I do
> generally put all the major trees over onto their own lvm filesystems -
> /usr, /var/, /home and swap,

Yes indeed. /usr because you shouldn't run / out of disk space merely
because you installed lots of stuff (and /usr tends to get all sorts of
strange things done to it); /var because it is written to a lot
(/var/log, /var/spool, /var/cache) so tends to go skewy before anything
else when the power suddenly dies or an electrical storm hits; /home
because it's easy to reinstall/upgrade without fear if /home is
somewhere the distro installer won't smash; swap because, well, there's
not such a good reason for that because configuring more swap is easy
and it doesn't matter (within reason) how many swap partitions you've
got. But it does let you *shrink* it if you configure too much and need
the space later on.
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