RE: Configuring for Online Redo Logfiles

Ed,List

Since we Enable log_checkpoint_interval to a Very High Value , Qs Would READs for Data of Tables Also NOT Occur from the Online Redo Logfiles ?

NOTE Oracle version 8.1.7.2

Thanks

> -----Original Message-----
> From: Edward Shevtsov [SMTP:ed_at_mb.ru]
> Sent: Thursday, November 15, 2001 7:16 PM
> To: Multiple recipients of list ORACLE-L
> Subject: Re: Configuring for Online Redo Logfiles
>
> Hi Vivek,
>
> If I didn't worry about data safety I would choose redo logs on
> dedicated
> single disks.
> The reason is that usually the speed of LGWR's writes is more
> important for
> performance compared with speed of ARCH's reads.
>
> Regards,
> Ed
>
>
> > Conor,List
> >
> > 1) Mirrored Redo Logs WRITES may have an Overhead of 15-20 %
> > EXCERPT from Gaja's Doc "One of the common myths with mirroring, is
> that
> > it takes "twice as long" to write.But in many performance
> measurements
> > and benchmarks, the overhead has been observed to be around 15-20%."
> >
> > 2) Mirrored Redo Logs READS are Twice as Fast than NON-Mirrored
> >
> > Considering BOTH the Above to POINTS , FINALLY Strictly w.r.t.
> > performance of Online Redo Logs , WITHOUT any Consideration for Data
> > Safety , Which would be Better ?
> >
> > Thanks
> >
> >
> > > -----Original Message-----
> > > From: Connor McDonald [SMTP:hamcdc_at_yahoo.co.uk]
> > > Sent: Thursday, November 15, 2001 3:15 PM
> > > To: Multiple recipients of list ORACLE-L
> > > Subject: Re: Configuring for Online Redo Logfiles
> > >
> > > An unmirrored disk will run faster (with respect to
> > > writes) than a mirrored one (not twice as fast since
> > > writes on a mirror are typically done in parallel).
> > > Then again - now you've got an unmirrored redo
> > > log...not a good idea. To get around this, you'd need
> > > to duplex it through Oracle - which pretty much gets
> > > you back to a "mirrored" redo log.
> > >
> > > hth
> > > connor
> > >
> > > --- VIVEK_SHARMA <VIVEK_SHARMA_at_infy.com> wrote: >
> > > EXCERPT from "Implementing Raid On Oracle Systems"
> > > > by Gaja Krishna
> > > > Vaidyanatha, Quest Software Inc. :-
> > > > "RAID 1 - Ideal for online and archived redo logs,
> > > > Leaves the write-head
> > > > at the location of the last write. On most systems,
> > > > you will need 3
> > > > volumes for the online redo logs (for 3 groups) and
> > > > 1 volume for the
> > > > archived redo logs. If your database is in
> > > > NOARCHIVELOG mode, you
> > > > probably can get away with a single RAID 1 volume
> > > > for your redo-logs.
> > > > However, for databases in ARCHIVELOG mode you will
> > > > need to further
> > > > separate you"
> > > > Qs. Puttting an Online Redo log on a RAID1 Volume (
> > > > Volume Containing 1
> > > > Disk Mirrored to Another Disk ) versus putting the
> > > > Same Online redo file
> > > > on a Single Disk (NON-Mirrored) , which would give
> > > > Better performance ,
> > > > Why ?
> > > > --
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Edward Shevtsov
> INET: ed_at_mb.ru
>
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Author: VIVEK_SHARMA
  INET: VIVEK_SHARMA_at_infy.com

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