Re: Effects of setting linux block device readahead size

On Thu, 11 Sep 2008, Scott Marlowe wrote:

> On Thu, Sep 11, 2008 at 3:36 PM, <david(at)lang(dot)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.

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.

David Lang