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Date: Thu, 21 Oct 2010 20:13:24 +0200
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Subject: Re: Slow count(*) again...
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On 2010-10-21 06:47, Scott Carey wrote:
>  On a wimpy disk, I/O bound for sure.   But my disks go 1000MB/sec.
>  No query can go fast enough for them.  The best I've gotten is
>  800MB/sec, on a wide row (average 800 bytes).  Most tables go
>  300MB/sec or so.  And with 72GB of RAM, many scans are in-memory
>  anyway.

Is it cpu or io bound while doing it?

Can you scan it faster using time cat relation-oid.* > /dev/null

>  A single SSD with supercapacitor will go about 500MB/sec by itself
>  next spring.   I will easily be able to build a system with 2GB/sec
>  I/O for under $10k.

What filesystem are you using? Readahead?
Can you try to check the filesystemfragmentation of the table using filefrag?

-- 
Jesper





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On 2010-10-21 06:47, Scott Carey wrote:<br>
<span style="white-space: pre;">&gt; On a wimpy disk, I/O bound for
sure.&nbsp;&nbsp; But my disks go 1000MB/sec.<br>
&gt; No query can go fast enough for them.&nbsp; The best I've gotten is<br>
&gt; 800MB/sec, on a wide row (average 800 bytes).&nbsp; Most tables go<br>
&gt; 300MB/sec or so.&nbsp; And with 72GB of RAM, many scans are in-memory<br>
&gt; anyway.<br>
</span><br>
<pre>Is it cpu or io bound while doing it?
</pre>
Can you scan it faster using time cat relation-oid.* &gt; /dev/null <br>
<span style="white-space: pre;"> <br>
&gt; A single SSD with supercapacitor will go about 500MB/sec by itself<br>
&gt; next spring.&nbsp;&nbsp; I will easily be able to build a system with 2GB/sec<br>
&gt; I/O for under $10k.<br>
<br>
</span>
<pre>What filesystem are you using? Readahead?
Can you try to check the filesystemfragmentation of the table using filefrag?

-- 
Jesper
</pre>
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