Fwd: AIX Concurrent I/O for Oracle archive logs
- From: David Roberts <big.dave.roberts@xxxxxxxxxxxxxx>
- To: oracle-l-freelists <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 25 May 2010 22:05:48 +0100
---------- Forwarded message ----------
From: David Roberts <big.dave.roberts@xxxxxxxxxxxxxx>
Date: Tue, May 25, 2010 at 10:05 PM
Subject: Re: AIX Concurrent I/O for Oracle archive logs
To: po04541@xxxxxxxxx
I will warn that this is a guess, all, abuse me at length!
Forgive me Alex!
With the appearance of Advanced format hard drives, Oracle has indicated
that they want to know the underlying disk physical file format for ASM file
systems and redo logs.
In the case of redo logs, it simply appears to be an attempt to begin redo
log buffer writes on block boundaries, theoretically reducing the number of
blocks written with each write, but obviously increasing the total number of
blocks written.
Thus I could see why holding redo logs on a file system with the same block
size as the underlying block size might improve performance, and there might
be a slight theoretical improvement in performance with regards archive redo
logs, I would suspect that the effect would be incredibly marginal!
Dave
On Tue, May 25, 2010 at 8:29 PM, patrick obrien <po04541@xxxxxxxxx> wrote:
> Allen,
>
> I too use AIX CIO and have been for years, for performance enhancement
> reasons.
>
> I've used these archives to rebuild my dev environment so I too know these
> are good.
>
> Patrick.
>
>
>
>
>
> --- On *Tue, 5/25/10, Allen, Brandon <Brandon.Allen@xxxxxxxxxxx>* wrote:
>
>
> From: Allen, Brandon <Brandon.Allen@xxxxxxxxxxx>
> Subject: AIX Concurrent I/O for Oracle archive logs
> To: "oracle-l@xxxxxxxxxxxxx" <Oracle-L@xxxxxxxxxxxxx>
> Date: Tuesday, May 25, 2010, 9:06 AM
>
>
> Hi List,
>
>
>
> Can anyone think of a good reason why Oracle’s archived redo logs shouldn’t
> be placed on a non-buffered (concurrent or direct IO) file system? Oracle
> Support document 418714.1 specifically states NOT to use DIO/CIO for file
> systems containing archive logs. However, I have one AIX system where my
> archive logs have been on a file system mounted with CIO for years and I’ve
> never had any problems (and yes, I’ve successfully used the logs for actual
> recovery).
>
>
>
> I’m considering moving another of my systems to CIO because on the other
> system, when archive log backups run, the AIX file system cache gets flooded
> by the archive logs and it has recently started causing the OS to start
> paging heavily, which in turn is bringing the system to a screeching halt
> for a few minutes, so I think if I move the logs to a CIO file system then
> they should no longer be read into the AIX buffer cache, and that should
> prevent this problem, but I just want to see if anyone has any good reasons
> why I should avoid using CIO with archive logs.
>
>
>
> Thanks,
>
> Brandon
>
>
>
>
>
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