Re: Redo Log Positioning

In article <957288168.15447.0.pluto.d4ee154e_at_news.demon.nl>,   "Sybrand Bakker" <postbus_at_sybrandb.demon.nl> wrote:
> IMO you have no other choice than to place the redologs on one raid 1
 disk,
> and the hard- or software mirror on the other raid 1 disk.
> As the redolog files are written sequentially there is no performance
 hit in
> placing all three on one drive. I usually start with 4 redo log
 groups, this
> layout seems less troublesome.
>
> Hth,
>
> Sybrand Bakker, Oracle DBA
>
> <rogerxb_at_my-deja.com> schreef in berichtnieuws
> 8emjtg$t78$1_at_nnrp1.deja.com...
> > I currently have two redo log files, unmirrored and sized at 2M
 each.
> > When we see intense processing there is a slow down and the error
 log
> > indicates that the bottleneck is the redo logs; they are unable to
> > complete archiving quickly enough when switching from redo 1 to
 redo 2.
> >
> > So I realize I have to re-work the system to at least increase the
 size
> > of the logs, and therefore switch less frequently.
> >
> > Here's my question.
> >
> > I have 5 physical 9.1 Gig drives - split into two raid sets -
> > 2 * 9.1 Gig Raid 1 and
> > 3 * 9.1 Raid 5.
> > The current redo logs are placed one on each of these separate
> > devices.
> > I understand that my Raid 5 is going to be slower when writing the
> > logs, but what I want to know is - how should I lay out my log
 files?
> > I believe The theoretical best is to have three groups with two
> > mirrored members in each, across at least three devices; but I only
> > have two physical devices and one is quicker than the other ......
 any
> > suggestions ??
> > Should I just increase the size of my logs, and allow the operating
> > system to do all the mirroring ???
> >
> > Cheers
> > Rog
> >
> >
> > Sent via Deja.com http://www.deja.com/
> > Before you buy.
>
>

While the writing from one log to the next is sequential, if you place them on the same physical device (regardless of any RAID or logical partitioning) wouldn't there be contention as one log file is being written while the previous one is being read for archive? Of course, this assume archive logmode.

--
Ed Stevens
(Opinions are not necessarily those of my employer)


Sent via Deja.com http://www.deja.com/
Before you buy.