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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Redo logs on mirrored disks
Chris-
I admire your bravery. Not once in my life have I had someone accidently = delete a redo log but I multiplex them religiously anyway.
Jim
>>> Chris_at_Royce.net 06/12/00 07:16PM >>>
I DO NOT multi-plex my redo logs BUT I have my entire production databases =
on
RAID 0+1 mirrored/striped detests. I had a nearly non recoverable =
situation
awhile back when I lost half a mirror on a duplexed redo log. I got into =
one of
those infuriating 'loops' while trying to drop a logfile 'member' which =
had the
missing 'half': cannot drop it because it doesn't exist, cannot use it =
because
it was missing etc. etc. Through a lot of experimenting and stressful =
gyrations
we were eventually able to trick the system into thinking it was a whole =
entity
and was able to 'drop' the logfile. I actually do not remember what I =
finally
did to get around it - must have repressed a potential data loss situation =
on a
production instance. I had another oddball situation that caused a =
performance
hit. Unbeknownst to me, half of my mirrored redo logs were on a different
controller and disk farm which was slightly older/slower. Everything ran =
fine
until we started generating significantly more redo. Seems that because of
unequal latency, every (approx.) 4 minutes it became necessary for the =
archiver
to catch up causing system interrupts and slowdowns. Took us weeks with =
software
and hardware people to identify the situation. Simple when you find out. =
Anyway
I eventually dropped the duplexed redos and the performance issue =
disappeared.
Then we discovered the hardware discrepancy.
Just my opinion. I now have 8 single set redo logs spread over 4 spindles =
of 250
MBytes each. I have had no problems and have not encountered any log =
switch
contingencies.
Thnx
Chris Royce
Snr DBA
Jamestown NC
Norwood Bradly A wrote:
> Robyn:
>
> Have not yet read that tip from Steve Adams, but I value his opinions =
very
> highly.
>
> However, Oracle seems to go with multiplexing as shown by their caveat
> regarding o/s or hardware corruption:
>
> In my shop, we do both mirroring and multiplexing
>
> Multiplexing Online Redo Log Files
> Oracle provides the capability to multiplex an instance's online redo =
log
> files to safeguard against damage.
> You can also mirror your redo logs at the O/S level, but in so doing you =
run
> the risk of O/S or hardware induced corruption. In most cases, multiplexi=
ng
> of online logs is best.
>
> -----Original Message-----
> Sent: Monday, June 12, 2000 11:52 AM
> To: Multiple recipients of list ORACLE-L
>
> listers,
>
> Reading through Steve Adams web site, I came across
> the tip that says redo logs should be mirrored or
> multiplexed, but there is no need to do both. The
> explanation makes sense, but I have never run a
> production database without multiplexing redo logs,
> and the thought of doing so is a little scary!! I
> wanted to find out how many other DBA's have taken
> this approach, and if you've tried it, how much of
> performance difference have you seen? Is there any
> increased risk of data loss?
>
> TIA ... Robyn Sands
>
> --
> Author:
> INET: rsands_at_lendleaserei.com=20
>
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> Author: Norwood Bradly A
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--=20
Author: Chris Royce
INET: Chris_at_Royce.net=20
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists --------------------------------------------------------------------To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may Received on Tue Jun 13 2000 - 07:41:40 CDT
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