Re: partition question for new server setup

Thanks to everyone who helped me arrive at the config for this server.
Here is my first set of benchmarks using the standard pgbench setup.

The benchmark numbers seem pretty reasonable to me, but I don't have a
good feel for what typical numbers are. Any feedback is appreciated.

-Whit

the server is set up as follows:
6 1TB drives all seagateBarracuda ES.2
dell PERC 6 raid controller card
RAID 1 volume with OS and pg_xlog mounted as a separate partition w/
noatime and data=writeback both ext3
RAID 10 volume with pg_data as xfs

nodeadmin(at)node3:~$ /usr/lib/postgresql/8.3/bin/pgbench -t 10000 -c 10
-U dbadmin test
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 100
number of clients: 10
number of transactions per client: 10000
number of transactions actually processed: 100000/100000
tps = 5498.740733 (including connections establishing)
tps = 5504.244984 (excluding connections establishing)
nodeadmin(at)node3:~$ /usr/lib/postgresql/8.3/bin/pgbench -t 10000 -c 10
-U dbadmin test
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 100
number of clients: 10
number of transactions per client: 10000
number of transactions actually processed: 100000/100000
tps = 5627.047823 (including connections establishing)
tps = 5632.835873 (excluding connections establishing)
nodeadmin(at)node3:~$ /usr/lib/postgresql/8.3/bin/pgbench -t 10000 -c 10
-U dbadmin test
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 100
number of clients: 10
number of transactions per client: 10000
number of transactions actually processed: 100000/100000
tps = 5629.213818 (including connections establishing)
tps = 5635.225116 (excluding connections establishing)
nodeadmin(at)node3:~$

On Wed, Apr 29, 2009 at 2:58 PM, Scott Carey <scott(at)richrelevance(dot)com> wrote:
>
> 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.
>
>