filesystem performance

[Mark Wong-3]

Hi everyone,

We (PostgreSQL community) have a HP DL380 G5 that we were using to do
some very basic filesystem characterizations as part of a database
performance tuning project, so we wanted to give FreeBSD a try out of
the box.  For this set of data we used 7.1.  We're (us few that are
running the tests) are fairly unfamiliar with the community here, so
I'll be as brief as I can.  We're basically wondering if the data
we're getting out of the box is expected, and any tuning guidelines
including what changes we should expect to see in the performance.

So that said, I'll start with some of the charted results:

Scaling from 1 device to 4 devices using RAID 0:
http://207.173.203.223/~markwkm/community10/fio/freebsd-7.1/raid0-ufs.png

Comparing RAID configurations of similar capacity:
http://207.173.203.223/~markwkm/community10/fio/freebsd-7.1/capacity-ufs.png

Comparing RAID configuration using same number of drives (4):
http://207.173.203.223/~markwkm/community10/fio/freebsd-7.1/4-disk-ufs.png

All of the raw data fio output, iostat, and vmstat including charts of
some of the iostat and vmstat data are buried in here:
http://207.173.203.223/~markwkm/community10/fio/freebsd-7.1/

We used fio v1.23 to run the tests and picked parameters based on what
PostgreSQL is capable of.  The profiles used are here:
http://git.postgresql.org/gitweb?p=performance-tuning.git;a=tree;f=contrib/freebsd/fio;h=5ae97420fba010a3685c12c24cd69266d83b4daf;hb=HEAD

Hardware details are here (note we only used 4 of the internal drives
for this test, none in the MSA 70, and you may notice we have a lit of
Linux data on this page too):
http://wiki.postgresql.org/wiki/HP_ProLiant_DL380_G5_Tuning_Guide#Hardware_Details

I know I've been brief and at the same time dumped a lot of raw data.
Any pointers to tuning guides that we have obviously not seen would be
a appreciated.  We hope this data is of interest and is helpful.

Regards,
Mark
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[Anthony Pankov]

Hello Mark,

May i ask a question while more expierenced people is waking up?

I don't fully understand the target. For what filesystem should be
optimized?

I expect a patterns of recorded IO calls when pgsql perform typical
operations with statistics and in-depth analysis.

Are you sure there is à strong relation between fio benchmark result and
PostgreSQL performance?

Tuesday, May 05, 2009, 9:30:47 AM, you wrote:

MW> Hi everyone,

MW> We (PostgreSQL community) have a HP DL380 G5 that we were using to do
MW> some very basic filesystem characterizations as part of a database
MW> performance tuning project, so we wanted to give FreeBSD a try out of
MW> the box.  For this set of data we used 7.1.  We're (us few that are
MW> running the tests) are fairly unfamiliar with the community here, so
MW> I'll be as brief as I can.  We're basically wondering if the data
MW> we're getting out of the box is expected, and any tuning guidelines
MW> including what changes we should expect to see in the performance.



--
Best regards,
 Anthony                            mailto:ap00@...


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[Florian Smeets]

On 05.05.09 07:30, Mark Wong wrote:

> Hi everyone,
>
> We (PostgreSQL community) have a HP DL380 G5 that we were using to do
> some very basic filesystem characterizations as part of a database
> performance tuning project, so we wanted to give FreeBSD a try out of
> the box.  For this set of data we used 7.1.  We're (us few that are
> running the tests) are fairly unfamiliar with the community here, so
> I'll be as brief as I can.  We're basically wondering if the data
> we're getting out of the box is expected, and any tuning guidelines
> including what changes we should expect to see in the performance.
>

I guess you are using the ciss driver in this box? There was a
performance regression in this driver in 7.1. This should be fixed in
7.2, which came out recently. It is believed that you should get a whole
lot better IO performance with 7.2 if you are using the ciss driver.

 From the 7.2 release notes:

A bug in the ciss(4) driver which caused low “max device openings” count
and led to poor performance has been fixed.

HTH,
Florian

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[Mark Wong-3]

On Wed, May 6, 2009 at 2:25 AM, Anthony Pankov <ap00@...> wrote:
> Hello Mark,
>
> May i ask a question while more expierenced people is waking up?
>
> I don't fully understand the target. For what filesystem should be
> optimized?
>
> I expect a patterns of recorded IO calls when pgsql perform typical
> operations with statistics and in-depth analysis.

The angle we're trying to look at is from a sizing perspective.  In
order words we want to have an idea of what to expect before we do it.
 For example, if I have 10 drives, what can I expect if I configure
them in a RAID 10 configuration?

> Are you sure there is ą strong relation between fio benchmark result and
> PostgreSQL performance?

Sorry, this was something I was trying to make clearer originally.
No, I don't think there is a strong relationship between fio and
PostgreSQL, but these i/o patterns we are simulating do give us a
rough estimate of we can expect.  For example, in workloads with lots
of update and inserts into a database will generate a lot of
sequential writes to the database logs, which we can physically
isolate onto it's own lun.  Similarly, in some warehousing
applications there may be a table that is always scanned and read
sequential, which also can be on its own physical lun.

Regards,
Mark
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[Mark Wong-3]

On Wed, May 6, 2009 at 7:18 AM, Florian Smeets <flo@...> wrote:

> On 05.05.09 07:30, Mark Wong wrote:
>>
>> Hi everyone,
>>
>> We (PostgreSQL community) have a HP DL380 G5 that we were using to do
>> some very basic filesystem characterizations as part of a database
>> performance tuning project, so we wanted to give FreeBSD a try out of
>> the box.  For this set of data we used 7.1.  We're (us few that are
>> running the tests) are fairly unfamiliar with the community here, so
>> I'll be as brief as I can.  We're basically wondering if the data
>> we're getting out of the box is expected, and any tuning guidelines
>> including what changes we should expect to see in the performance.
>>
>
> I guess you are using the ciss driver in this box? There was a performance
> regression in this driver in 7.1. This should be fixed in 7.2, which came
> out recently. It is believed that you should get a whole lot better IO
> performance with 7.2 if you are using the ciss driver.
>
> From the 7.2 release notes:
>
> A bug in the ciss(4) driver which caused low “max device openings” count and
> led to poor performance has been fixed.

We'll have to make time to try that. :)  Thanks (and to the others)
for pointing that out.

Regards,
Mark
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