[sclug] Newbie, partitioning 120Gb HDD - recommendations?

[James Fidell]

Quoting Alex Butcher (lug at assursys.co.uk):
> On Tue, 18 Jan 2005, David Newcomb wrote:
> 
> > When the machine boots up the partition table is read.
> > For each partition there is a superblock which contains all the inodes
> > and addressing information for that partition.
> >
> > If you have 1 root partition at the start and (therefore faster outermost
> > rim of the disc) then everything that needs to be read or writen can
> > be accessed extremly fast. Only 1 super node structure is held in memory.
> > All the information can be read in a series of sequental reads.
> >
> > If you have serveral partitions then there is a superblock structure
> > for each of the partitions, which are spread across the whole disc.
> > Read & write operations cause the disc heads to jump to each of the
> > superblock structures for each partition as they read and write.
> 
> Naw, I still don't buy it.

Nor I. It's just not that simple. As the size of a partition increases,
lots of other data structures increase in size, too, both on the disk
and in memory. Some of those come with orders-of-magnitude performance
penalties once given limits are passed. Try running something like a
large USENET spool, which has a very random access pattern, for example,
and you'll rapidly see what I'm talking about.

For what it's worth, for desktop boxes I never bother setting up lots
of partitions.  I've never found any major value in doing otherwise,
but then I never keep anything "mission critical" on my desktop machine.

For servers that *are* mission critical however, I always put important
data in its own partition.  There's no way I want something unrelated
happening on the server to cause that data to get corrupted.  For instance,
I don't want some process to start spewing stuff into the logs causing
(say) mysql to run out of disk space, corrupting its index files
and stopping service to users.   Or something dumping a large file
in /var/tmp causing email to stop working.  There are loads of other
reasons for setting up multiple partitions relating to performance,
security and cost that I just don't have time to go into.

The bottom line is that there is no "correct" way to partition a disk.
You need to look at how the machine is going to be used, decide how you
want it to work, including how you want to protect yourself from the
things that go wrong, and take it from there.  You can't take any single
issue in isolation and expect to get an optimal result.

James