RE: I/O and db_file_multiblock_read

From: Kevin Closson <kevinc_at_polyserve.com>
Date: Mon, 11 Dec 2006 13:38:39 -0800
Message-ID: <5D2570CAFC98974F9B6A759D1C74BAD001C33776@ex2.ms.polyserve.com>

I have found that I/O requests that involve the same spindles more than onec in a single
request simply do not perform. It is generally better to hit the LUN more times for I/Os
sized rightly to not wrap an entire stripe set.

So, if I have 2 disks and intend to scan them with 1MB reads, uh, I don't set the stripe
width to 32KB. Having the array line up 16 chucks on each disk to satisfy a single
transfer request is just a mess.

In fact, I generally set stripe width to a value larger than 1MB if the kit supports it.

YMMV ... this is a religious topic you know... :-)

	From: Vlad Sadilovskiy [mailto:vlovsky_at_gmail.com] 
	Sent: Monday, December 11, 2006 1:29 PM
	To: kevinc_at_polyserve.com
	Cc: oracle-l
	Subject: Re: I/O and db_file_multiblock_read_count
	
	
	How does number of disk hits for larger I/O corresponds to

number of hits for smaller I/O in respect to the whole process. It should not be more should it? Unless same data gets read twice.

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Received on Mon Dec 11 2006 - 15:38:39 CST

RE: I/O and db_file_multiblock_read_count