Re: Mirroring redo log groups or not ?
Date: Tue, 7 Apr 2009 14:21:52 -0400
Message-ID: <69eafc3f0904071121o11c906e7j154694c97d992ba_at_mail.gmail.com>
Mirroring protects you from more than disk failure, it also protects you from human error. Please, mirror your logs. There is a long history littered with un-employed DBAs backing this recommendation.
For your specific problem, you might want to look a a couple of things. How long does it take you to fill up a gigabyte of redo? How long does it take you to write an archive log that's a gigabyte in size? What is your log_buffer parameter set to? Have you evaluated the effect of checkpoints in your situation?
On Tue, Apr 7, 2009 at 1:14 PM, Crisler, Jon <Jon.Crisler_at_usi.com> wrote:
> The redo logs are 6 groups, 2 members each, 1gb in size. The SAN is EMC
> Clariion. Raid 5 does have somewhat poorer performance in writes in our
> environment but its usually not a major factor.
>
> -----Original Message-----
> From: Rajeev Prabhakar [mailto:rprabha01_at_gmail.com]
> Sent: Tuesday, April 07, 2009 12:48 PM
> To: Crisler, Jon
> Cc: Oracle-L Freelists
> Subject: Re: Mirroring redo log groups or not ?
>
> Hello Jon,
>
> Before you go into redesign of the redo logs, did you check w/the
> SAs/Storage
> Admins ? During my last interactions with type of performance issue, I
> found
> that RAID 5 had a negative effect on overall performance during QA
> testing. of
> course, your mileage may vary.
>
> Can you share your findings (as seen by SA/Storage Admins). How big are
> your
> redo logs ? What kind of disks (Storage/SAN) are you folks using ?
>
> -Rajeev
>
> On Tue, Apr 7, 2009 at 12:16 PM, Crisler, Jon <Jon.Crisler_at_usi.com>
> wrote:
>
> > So, if the LUN that holds the online redo logs is already protected
> (raid 1,
> > 5 etc) do I really need to mirror the online redo logs ? Should I
> convert
> > the LUN to Raid 1 / 0 ? if I convert to Raid 1/ 0 should I keep redo
> log
> > mirroring and point to the same LUN ?
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>
-- http://www.freelists.org/webpage/oracle-lReceived on Tue Apr 07 2009 - 13:21:52 CDT