Re: REDO Logs - 3rd mirror?

"Paul Drake" <drak0nian_at_yahoo.com> wrote in message news:1ac7c7b3.0301251249.76ac81f8_at_posting.google.com...
> "JustAnotherDBA" <jadba_at_bellsouth.net> wrote in message
news:<sBpX9.58033$Jm2.54069_at_news.bellsouth.net>...
> > UPS maintenance caused power to flicker off and on several times to our
main
> > Oracle production server causing the loss of 5 disk drives in 1 RAID
array -
> > 4 of which were used to hold just the REDO logs for 2 of 3 databases.
These
> > 2 Oracle databases were setup to multiplex on 2 RAID1 (mirrored) disks.
This
> > is a large Unix server, SunFire V880 8CPUs with 4 RAID A1000s (total
disks
> > about 54) and running Oracle8i 8.1.7.3 and 8.1.7.4 . The 3rd database
is on
> > totally separate RAID arrays with its own Oracle Home software and
hardly
> > missed a beat - 15 minutes to reboot.
> <snip>
> > Does anyone else even use a 3rd multiplex REDO member ? I haven't ,
but
> > will probably do this especially considering the current 2 RAID1 mirrors
are
> > in 1 array.
> >
>
> HJR seems to think so (3 log members per redo log group) and posts as
> such quite frequently. I haven't been able to justify that
> configuration on w2k boxen yet ... but I do duplex.

I only recommend 3 because I get nervous with 2! There are (or I should rather say ' are likely to be') performance impacts from triplexing your redo, and those have to be taken into account before blindly making the move from duplexing (though raw can help).

Mind you, there are performance impacts from switching logs, too. So if you're forcing a log switch every X minutes, that might need to be weighed up against no-switch-triplexing.

Gut feel would be, however, that duplexing into two RAID volumes would probably be sufficient. But I'd probably be looking, even so, at using 9i and LGWR to pass off the redo to a remote site. But then the [potential] performance impacts get even more worrisome.

As ever, it all depends.

Regards
HJR Received on Tue Jan 28 2003 - 10:40:00 CST