Re: RE: linux DBA's: O_Direct
- From: MARK BRINSMEAD <mark.brinsmead@xxxxxxx>
- To: kevinc@xxxxxxxxxxxxx
- Date: Wed, 23 Nov 2005 16:06:23 -0700
Ah. It seems that my memory *is* failing me. The parameter I was thinking of
was NOT "BUFFERMEM" (which is no doubt long obsolete) but rather PAGECACHE.
Adding the entry:
vm.pagecache 5 15 10
to /etc/sysctl.conf should (if I *now* recall correctly) set the minimum,
maximum, and "target" filesystem buffers to 5%, 15%, and 10% of RAM
respectively.
The object /proc/sys/vm/pagecache does, indeed, exist on my RHEL3 servers, so I
will take that to be a hint that I have got it right this time. It seems that
I may have delegated sysadmin work to others for too long now, so I shall leave
it to the "gurus" on the list to confirm or deny this...
In the meantime, I think I will refrain from posting to this list while sitting
at home watching "House M.D."; it does not seem to improve the quality of my
input...
Cheers,
-- Mark.
----- Original Message -----
From: Kevin Closson <kevinc@xxxxxxxxxxxxx>
Date: Tuesday, November 22, 2005 10:57 pm
Subject: RE: linux DBA's: O_Direct
> >>>>I run database backups to an ext3 filesystem, using both
> >>>rman and regular hotbackups on different servers. Linux uses
> >>>all available ram to cache the writes to ext3, which can
>
> If this is RMAN, why isn't oracle using O_DIRECT for the ext3 target?
>
> 10gR2 will do open(,O_DIRECT,) on ext3 if you set
> filesystemio_options=directIO.
> I would recommend doing that, but then I'd also recommend a
> filesystem where you can put any thing you please
> in there - without the worry of landmines to step on...none of this
> "Uh, I think I'll put some goodies in ocfs filesystem, but then
> I have to put these other goodies in ext3 so my system doesn't
> blow up"
>
>
> Kevin Closson
> Chief Architect, Database Solutions
> PolyServe
> www.polyserve.com
>
>
>
> >>>reduce free memory to 10-20MB (the box has 12GB) - this is
> >>>how it is supposed to work. Sometimes the kernel is unable
> >>>to allocate ram for new processes when it drop to this level
> >>>and causes errors. It seems to me that filesystem block
> >>>caching is unsuitable for a database server - it is not an
> >>>issue for OCFS, only for backups to ext3.
> >>>>
> >>>>[...]
> >>>>--
> >>>>
> >>>>
> >>>
> >>>--
> >>>//www.freelists.org/webpage/oracle-l
> >>>
> >>>
> >>>
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
--
//www.freelists.org/webpage/oracle-l
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