RE: FRA f/s block size
- From: "Amaral, Rui" <Rui.Amaral@xxxxxxxxxxxxxxxx>
- To: "'dbvision@xxxxxxxxxxxx'" <dbvision@xxxxxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 28 Mar 2011 07:15:43 -0400
For rhel 6 (similar in previous versions as well):
http://people.redhat.com/msnitzer/docs/io-limits.txt
more detail on the block devices files in sysfs:
http://www.mjmwired.net/kernel/Documentation/ABI/testing/sysfs-block
looking at queue size might help performance (depending on your i/o scheduler
being used):
http://yoshinorimatsunobu.blogspot.com/2009/04/linux-io-scheduler-queue-size-and.html
one form of linux block tracing:
http://linux.die.net/man/8/blktrace
and example:
http://kb.fusionio.com/KB/a27/howto-capture-a-block-trace-in-linux.aspx
good ole strace also can give io and blocksize requests on running processes.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Nuno Souto
Sent: Monday, March 28, 2011 5:32 AM
To: oracle-l@xxxxxxxxxxxxx
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@xxxxxxxxxxxx
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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