Re: suggestions for postgresql setup on Dell 2950 , PERC6i controller

Detailed bonnie++ figures.

http://98.129.214.99/bonnie/report.html

On Wed, Feb 18, 2009 at 1:22 PM, Rajesh Kumar Mallah
<mallah(dot)rajesh(at)gmail(dot)com> wrote:
> the raid10 voulme was benchmarked again
> taking in consideration above points
>
> # fdisk -l /dev/sda
> Disk /dev/sda: 290.9 GB, 290984034304 bytes
> 255 heads, 63 sectors/track, 35376 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
>
> Device Boot Start End Blocks Id System
> /dev/sda1 * 1 12 96358+ 83 Linux
> /dev/sda2 13 1317 10482412+ 83 Linux
> /dev/sda3 1318 1578 2096482+ 83 Linux
> /dev/sda4 1579 35376 271482435 5 Extended
> /dev/sda5 1579 1839 2096451 82 Linux swap / Solaris
> /dev/sda6 1840 7919 48837568+ 83 Linux
> /dev/sda7 29297 35376 48837600 83 Linux
>
>
> CASE writes reads
> KB/s KB/s
>
> ext3(whole disk) 244194 , 352093 one part whole disk
> xfs(whole disk) 402352 , 547674
>
> 25ext3 260132 , 420905 partition only first 25%
> 25xfs 404291 , 547672 (/dev/sda6)
>
> ext3_25 227307, 348237 partition
> specifically last 25%
> xfs25 350661, 474481 (/dev/sda7)
>
>
> Effect of ReadAhead Settings
> disabled,256(default) , 512,1024
>
> xfs_ra0 414741 , 66144
> xfs_ra256 403647, 545026 all tests on sda6
> xfs_ra512 411357, 564769
> xfs_ra1024 404392, 431168
>
> looks like 512 was the best setting for this controller
>
> Considering these two figures
> xfs25 350661, 474481 (/dev/sda7)
> 25xfs 404291 , 547672 (/dev/sda6)
>
> looks like the beginning of the drives are 15% faster
> than the ending sections , considering this is it worth
> creating a special tablespace at the begining of drives
>
> if at all done what kind of data objects should be placed
> towards begining , WAL , indexes , frequently updated tables
> or sequences ?
>
> regds
> mallah.
>
>>On Tue, Feb 17, 2009 at 9:49 PM, Scott Carey <scott(at)richrelevance(dot)com> wrote:
>> Generally speaking, you will want to use a partition that is 25% or less the size of the whole disk as well. If it is >the whole thing, one file system can place the file you are testing in a very different place on disk and skew results as well.
>>
>> My own tests, using the first 20% of an array for all, showed that xfs with default settings beat out or equalled >'tuned' settings with hardware raid 10, and was far faster than ext3 in sequential transfer rate.
>
> same here.
>
>>
>> If testing STR, you will also want to tune the block device read ahead value (example: /sbin/blockdev -getra
>> /dev/sda6). This has very large impact on sequential transfer performance (and no impact on random access). >How large of an impact depends quite a bit on what kernel you're on since the readahead code has been getting >better over time and requires less tuning. But it still defaults out-of-the-box to more optimal settings for a single >drive than RAID.
>> For SAS, try 256 or 512 * the number of effective spindles (spindles * 0.5 for raid 10). For SATA, try 1024 or >2048 * the number of effective spindles. The value is in blocks (512 bytes). There is documentation on the >blockdev command, and here is a little write-up I found with a couple web searches:
>>http://portal.itauth.com/2007/11/20/howto-linux-double-your-disk-read-performance-single-command
>
>
>>
>> ________________________________________
>> From: pgsql-performance-owner(at)postgresql(dot)org [pgsql-performance-owner(at)postgresql(dot)org] On Behalf Of Rajesh Kumar Mallah [mallah(dot)rajesh(at)gmail(dot)com]
>> Sent: Tuesday, February 17, 2009 5:25 AM
>> To: Matthew Wakeling
>> Cc: pgsql-performance(at)postgresql(dot)org
>> Subject: Re: [PERFORM] suggestions for postgresql setup on Dell 2950 , PERC6i controller
>>
>> On Tue, Feb 17, 2009 at 5:15 PM, Matthew Wakeling <matthew(at)flymine(dot)org> wrote:
>>> On Tue, 17 Feb 2009, Rajesh Kumar Mallah wrote:
>>>>
>>>> sda6 --> xfs with default formatting options.
>>>> sda7 --> mkfs.xfs -f -d sunit=128,swidth=512 /dev/sda7
>>>> sda8 --> ext3 (default)
>>>>
>>>> it looks like mkfs.xfs options sunit=128 and swidth=512 did not improve
>>>> io throughtput as such in bonnie++ tests .
>>>>
>>>> it looks like ext3 with default options performed worst in my case.
>>>
>>> Of course, doing comparisons using a setup like that (on separate
>>> partitions) will skew the results, because discs' performance differs
>>> depending on the portion of the disc being accessed. You should perform the
>>> different filesystem tests on the same partition one after the other
>>> instead.
>>
>> point noted . will redo the test on ext3.
>>
>>
>>>
>>> Matthew
>>>
>>> --
>>> "We did a risk management review. We concluded that there was no risk
>>> of any management." -- Hugo Mills <hugo(at)carfax(dot)nildram(dot)co(dot)uk>
>>>
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>