Re: partition question for new server setup

On 4/29/09 7:28 AM, "Whit Armstrong" <armstrong(dot)whit(at)gmail(dot)com> wrote:

> Thanks, Scott.
>
>> I went with ext3 for the OS -- it makes Ops feel a lot better. ext2 for a
>> separate xlogs partition, and xfs for the data.
>> ext2's drawbacks are not relevant for a small partition with just xlog data,
>> but are a problem for the OS.
>
> Can you suggest an appropriate size for the xlogs partition? These
> files are controlled by checkpoint_segments, is that correct?
>
> We have checkpoint_segments set to 500 in the current setup, which is
> about 8GB. So 10 to 15 GB xlogs partition? Is that reasonable?
>

Yes and no.
If you are using or plan to ever use log shipping you¹ll need more space.
In most setups, It will keep around logs until successful shipping has
happened and been told to remove them, which will allow them to grow.
There may be other reasons why the total files there might be greater and
I'm not an expert in all the possibilities there so others will probably
have to answer that.

With a basic install however, it won't use much more than your calculation
above.
You probably want a little breathing room in general, and in most new
systems today its not hard to carve out 50GB. I'd be shocked if your mirror
that you are carving this out of isn't at least 250GB since its SATA.

I will reiterate that on a system your size the xlog throughput won't be a
bottleneck (fsync latency might, but raid cards with battery backup is for
that). So the file system choice isn't a big deal once its on its own
partition -- the main difference at that point is almost entirely max write
throughput.