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Message-ID: <dcc563d10809111930g10fc5256wac2020d596e3474d@mail.gmail.com>
Date: Thu, 11 Sep 2008 20:30:38 -0600
From: "Scott Marlowe" <scott.marlowe@gmail.com>
To: david@lang.hm
Subject: Re: Effects of setting linux block device readahead size
Cc: "Scott Carey" <scott@richrelevance.com>,
	"James Mansion" <james@mansionfamily.plus.com>,
	"Greg Smith" <gsmith@gregsmith.com>, pgsql-performance@postgresql.org
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On Thu, Sep 11, 2008 at 4:33 PM,  <david@lang.hm> wrote:
> On Thu, 11 Sep 2008, Scott Marlowe wrote:
>
>> On Thu, Sep 11, 2008 at 3:36 PM,  <david@lang.hm> wrote:
>>>
>>> by even if it didn't, most modern drives read the entire cylinder into
>>> their
>>> buffer so any additional requests to the drive will be satisfied from
>>> this
>>> buffer and not have to wait for the disk itself.
>>
>> Generally speaking I agree, but I would still make a separate logical
>> partition for pg_xlog so that if the OS fills up the /var/log dir or
>> something, it doesn't impact the db.
>
> this is a completely different discussion :-)
>
> while I agree with you in theory, in practice I've seen multiple partitions
> cause far more problems than they have prevented (due to the partitions
> ending up not being large enough and having to be resized after they fill
> up, etc) so I tend to go in the direction of a few large partitions.

I've never had that problem.  I've always made the big enough.  I
can't imagine building a server where /var/log shared space with my
db.  It's not like every root level dir gets its own partition, but
seriously, logs should never go anywhere that another application is
writing to.

> the only reason I do multiple partitions (besides when the hardware or
> performance considerations require it) is when I can identify that there is
> some data that I would not want to touch on a OS upgrade. I try to make it
> so that an OS upgrade can wipe the OS partitions if nessasary.

it's quite handy to have /home on a separate partition I agree.  But
on most servers /home should be empty.  A few others like /opt or
/usr/local I tend to make a separate one for the reasons you mention
as well.