Re: FRA f/s block size

From: Nuno Souto <dbvision_at_iinet.net.au>
Date: Mon, 28 Mar 2011 20:32:19 +1100
Message-ID: <4D9055A3.2050806_at_iinet.net.au>



Thanks Yechiel. That's my gut feel as well.

The only minor snag I can see is that AFAIK the actual I/O size used by RMAN is not documented anywhere. If it is doing 512 units in scatter/gather I/O, then it's virtually the same as 8K blocks - assuming the db is 8k.

Given that it is mostly doing big sequential as you note, it shouldn't matter at all if the last block gets half-filled in case it's doing 8k block I/O.

Ah, I wish I had in Unix the ability to trace actual raw I/O sizes no matter what, like I could in the mainframes...

-- 
Cheers
Nuno Souto
in sunny Sydney, Australia
dbvision_at_iinet.net.au



Yechiel Adar wrote,on my timestamp of 28/03/2011 5:52 PM:

> No experience, just a thought.
> It is used for big sequential writes and no random reads or writes.
> In this case I will used the biggest block I can to minimize the I/Os to the disk.
>
> The reason we use small blocks is to minimize the redundant data transferred to
> memory when you need only one record in the block.
> When you write or read whole blocks, in big sets, use the block size that will
> minimize I/O.
>
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Received on Mon Mar 28 2011 - 04:32:19 CDT

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