Re: Optimal settings for embedded system running PostgreSQL

Have you considered switching to embedded Linux instead of XP?

This has the potential to help increase performance, as embedded Linux
will most likely have a smaller footprint.

Give this a read:
http://www.lynuxworks.com/products/whitepapers/xp-vs-linux.php3

Of course, if you're using an application which is completely reliant
on Windows, this may not be cost feasible.

But, if you application is Java based, as many embedded applications
are, the transition from XP to Linux could be pretty simple.

Ken

On Thu, Jan 13, 2011 at 11:31 AM, Christian Walter
<embedded(dot)solutions(dot)at(at)gmail(dot)com> wrote:
>> ________________________________
>> Von: pgsql-general-owner(at)postgresql(dot)org im Auftrag von Ivan Voras
>> Gesendet: Do 13.01.2011 15:47
>> An: pgsql-general(at)postgresql(dot)org
>> Betreff: Re: [GENERAL] Optimal settings for embedded system running
>> PostgreSQL
>>
>> On 13/01/2011 14:30, Christian Walter wrote:
>>>
>>> Dear Members,
>>>
>>> We are currently using PostgreSQL 7.3 on an Embedded System (Based on
>>> http://www.msc-ge.com/de/produkte/com/qseven/q7-us15w.html) running
>>> Windows XP Embedded / SP3. The onbard flash shows the following
>>> performance figures:
>
> This was a typo. Of course we are using PostgreSQL 8.3 and not 7.3.
>
>>>
>>> - Average read = 15,6Mb/s
>>> - 4Kbyte reads = 3,5Mb/s
>>> - 1Kbyte read = 1Mb/s
>>
>> This is very slow. Have you considered something more light-weight like
>> SQLite?
>
> This is comparable to a standard USB2.0 flash drive. Reads are faster
> on very large block sizes but I thought postgres by default uses
> 8Kbyte. At 8KByte we have about 5000kbyte/s. For example if you
> compare a standard flash disk, e.g.
> http://www.innodisk.com/production.jsp?flashid=34 so can see that they
> specify 26mb/sec as a max. The same is specified here but I think is
> is only for very large block sizes. Using a different database is not
> an option for us since our software depends on PostgreSQL and on its
> JDBC drivers. We are working with the vendor to find a solution for
> this but of course this is only a long term option.
>
>>> We are sometimes facing problems that the system seems to hang due to
>>> database activity and now we are looking to improve the situation. If
>>> the database application is running and we run the benchmark again
>>> figures drop down to zero so we assume that the database (and
>>> application) is responsible for the high load. Since the embedded flash
>>> is quite hard to change we are looking for solution on improving this.
>>> For me it seems that blocksize seems a big issue and I would like to
>>> know if a recompile of Postgres with a larger block size would resolve
>>> this?
>>
>> You can, see --with-blocksize and --with-wal-blocksize arguments to
>> ./configure, but flash memory is notorious for having really large block
>> sizes, on the order of 256 KiB - I suspect it would be very inefficient
>> if the database tried to do everything in such large blocks.
>
> I think increasing to 32Kbyte would not be a problem because 8KByte is
> the default. If this can give us some benefit I am willing to give it
> a try and recompile the software using VS2005.
>
>>
>>> Are there any other options which should be set for flash based disks
>>> since latency is a lower than on harddisks.
>>
>> First, you need to confirm or find where the real problem is. Windows is
>> hard for debugging but you may get some information from the "perfmon"
>> applet.
>
> We have already planned to use perfmon for this task to double check
> if its really IO related. I am sure for about 60% because a parallel
> harddisk bench shows a decrease in performance when this happens.
>
>>
>>
>>
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>
>
> --
> --
> +--------------------------------------+-----------------------------------+
> Embedded Solutions                     | DI Christian Walter
> Lorenz Böhler Gasse 4/4, A-1200 Wien   | cwalter(at)embedded-solutions(dot)at
> http://www.embedded-solutions.at       | +43-664-2486048
>
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