Re: single session I/O bandwidth
Date: Thu, 14 Mar 2013 10:04:27 -0700 (PDT)
Message-ID: <1363280667.96986.YahooMailNeo_at_web162803.mail.bf1.yahoo.com>
not if it is in the buffered path..if buffered then OS block readahead will kick in.
If you want to know what Oracle can do with storage, use Oracle. Not synthetic I/O tools like dd. (not preaching at you here, Noons. Just reminding the list)
http://kevinclosson.wordpress.com/2013/03/03/my-oaktable-world-2012-video-session-is-now-online/
I monitored this thread and only one participant chimed in on the real problem which is CPU. Oracle can do I/O without burning CPU with CALIBRATE. Any other method for driving physical I/O will burn CPU. Even count(*) has memory loads of the block hear to get the slot count. If not parallel, even a count(*) will be CPU-bound.
From: Nuno Souto <dbvision_at_iinet.net.au> To: oracle-l_at_freelists.org
Sent: Tuesday, March 12, 2013 2:59 AM
Subject: Re: single session I/O bandwidth
and if you use dd, don't forget to set bs, ibs or obs to 8K or whatever
the db block size is..
Otherwise you'll be measuring times for 512 byte I/O.
-- Cheers Nuno Souto dbvision_at_iinet.net.au On 12/03/2013 6:05 PM, Iggy Fernandez wrote:Received on Thu Mar 14 2013 - 18:04:27 CET
> Why is the basis of the assumption that a single Oracle thread has more capacity that that? Trace one of the threads for a while using "strace -c" to produce a summary and you will see how time is spent within the thread.
> You can also check a summary trace of a "dd of=/dev/null" command. Chances are you will see higher throughput but dd much less processing than an Oracle thread.
> Kindest regards,
>
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