RE: FRA f/s block size
Date: Mon, 28 Mar 2011 07:15:43 -0400
For rhel 6 (similar in previous versions as well):
more detail on the block devices files in sysfs:
looking at queue size might help performance (depending on your i/o scheduler being used):
one form of linux block tracing:
good ole strace also can give io and blocksize requests on running processes.
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Nuno Souto Sent: Monday, March 28, 2011 5:32 AM
Subject: Re: FRA f/s block size
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:Received on Mon Mar 28 2011 - 06:15:43 CDT
> 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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