Re: asynch I/O

I just hit a description of async IO in Oracle docs, it is very simply described there:

<quote>
With synchronous I/O, when an I/O request is submitted to the operating system, the writing process blocks until the write is confirmed as complete. It can then continue processing.
Asynchronous I/O allows a process to submit an I/O request but to then continue processing. It may then check on the result of the I/O at a later time. It is also possible to submit several I/O requests and then collect the status of those requests at a later time, thus allowing the operating system to parallelize any of those I/O operations, where possible. Parallel processing can reduce the overall time to complete an operation.

Consider an extreme example: Imagine you want to write out four data blocks to four different files. With synchronous I/O you must submit block 1, wait, submit block 2, wait, submit block 3, wait, submit block 4, and wait. With asynchronous I/O, you can submit blocks 1, 2, 3, and 4 and then wait for all four blocks to complete. Because you gave the operating system all four I/O requests at once, it can act on all the requests in parallel. The total response time is only the duration of the longest I/O of the four, rather than the sum of all four I/O durations.

</quote>

Tanel.

• Original Message -----

To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Friday, September 19, 2003 5:24 PM

> Ryan,
>
> You can have separate mount points from your server's perspective, but
once you get into the NetApp it's just a pool of disk drives that are allocated as necessary by their WAFL (Write Anywhere File Layout) system. Therefore in reality you get zero benefit.
>
> Dick Goulet
> Senior Oracle DBA
> Oracle Certified 8i DBA
>
> -----Original Message-----
> Sent: Thursday, September 18, 2003 10:10 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Could you clarify something for me? Are you saying that if I have a
variety
> of 'mounts' on our netapp
>
> say
>
> /mnt1
> /mnt2
>
> I would not benefit by putting my datafiles on seperate ones? I thought
that
> is where my I/O waits are coming from. Since we have all of our datafiles
in
> the same directory?
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Ryan
> INET: rgaffuri_at_cox.net
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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