Avoid RAID-5 on Redo Logs- WHY?

Hello all,
I read that, one should avoid using RAID Level 5 on Redo Log Files. Can anyone help me make understand this concept?
Why it is recommended so?
Also, it will be a great help if you can provide me articles explaining the various levels of RAID and their effect/significance on database.
Thanks in advance.
Himanshu

In general, RAID usually impacts write operations more than read operation.
This is specially true where parity need to be calculated (RAID 3, RAID 5, etc).
Online or archived redo log files can be put on RAID 1 devices.
You should not use RAID 5. 'TEMP' tablespace data files should also go on
RAID1 instead of RAID5 as well. The reason for this is that streamed
write performance of distributed parity (RAID5) isn't as good as that of
simple mirroring (RAID1).
Jaffar

Similar Messages

Online redo logs fill-up due to long running SCM processes

DB2 v9.7
AIX v6.1 P570
Running Standard SAP Code
Going live with SCM system running SNP/DP GATP how can we avoid having our online redo logs fill-up due to long running processes (i.e., CTM. Process Chains, BOP, DP Runs) Need to know SAP Best Practice regarding this -
Per our developers, BOP jobs performs commit when everything is processed and update table in one go at end, Hence not possible to perform commit regularly. Actually they will have to run BOP for 3200 material with 98000 sales order items.
But after just running BOP for 40 material with 22000 sales orders line items we are getting DBIF_RSQL_SQL_ERROR + CX_SY_OPEN_SQL_DB dumps
Any assistance on this would be helpful...
Thanks -

Fred
Check OSS notes for this error. The BOP compponent has a steady stream of corrections developed by SAP especially in older releases.
Also make sure your Livecache Build is consistent with SCM Release/ Patch level.
Rishi Menon

Why do we need standby redo log on Primary database.

Hi Gurus,
I was going through the document in OBE,
http://www.oracle.com/technology/obe/11gr1_db/ha/dataguard/physstby/physstdby.htm
I have two queries:
1) I noticed the statement -
"Configure the primary database to receive redo data, by adding the standby logfiles to the primary. "
Why do we have to create standby redo log on a primary database?
2) There is another statement --
"It is highly recommended that you have one more standby redo log group than you have online redo log groups as the primary database. The files must be the same size or larger than the primary database’s online redo logs. "
Why do we need one additional standby redo log group than in Primary database.
Could anyone please explain to me in simple words.
Thanks
Cherrish Vaidiyan

Hi,
1. Standby redo logs are used only when the database_role is standby, it is recommended to be added in primary also so that they can be used on role reversal, however during normal working standby redo logs will not be used at all on primary.
2. In case of 3 online redo log groups, it is recommended to use 4 standby redo log group this is in case if log switching is happening frequently on primary and all 3 standby redo logs are still not completely archived on the standby and 4th can be used here as there will be some delay on standby due to network or slowness of arch on standby.
Use of the standby redo log groups depends on the redo generation rate, you can see only 2 standby redo logs are getting used while you have 4 standby redo log groups, when the redo generation rate is less.
So it is recommended to have one more standby redo log group when redo generation rate is high and all of the existing standby redo log group are getting used.
Regards
Anudeep

Why it automatically recover current redo log in RMAN command window?

Firstly, I restore controlfile and datafiles from a backupset.
Then when I recover database in RMAN command window like below:
RMAN> recover database;
Starting recover at 15-AUG-13
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=156 devtype=DISK
starting media recovery
archive log thread 1 sequence 9 is already on disk as file /u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_9_90sd0slz_.arc
archive log thread 1 sequence 10 is already on disk as file
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_10_90sd0tsb_.arc
archive log thread 1 sequence 11 is already on disk as file
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_11_90sd110b_.arc
archive log thread 1 sequence 12 is already on disk as file
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_12_90sd2ksr_.arc
archive log thread 1 sequence 13 is already on disk as file
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_13_90sd2mc6_.arc
archive log thread 1 sequence 14 is already on disk as file
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_14_90sd2qrm_.arc
archive log thread 1 sequence 15 is already on disk as file
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_15_90sd2s0w_.arc
archive log thread 1 sequence 16 is already on disk as file /u01/app/oracle/oradata/lonion/redo03.log
archive log filename=/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_9_90sd0slz_.arc thread=1 sequence=9
archive log filename=/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_10_90sd0tsb_.arc thread=1 sequence=10
archive log filename=/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_11_90sd110b_.arc thread=1 sequence=11
archive log filename=/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_12_90sd2ksr_.arc thread=1 sequence=12
archive log filename=/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_13_90sd2mc6_.arc thread=1 sequence=13
archive log filename=/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_14_90sd2qrm_.arc thread=1 sequence=14
archive log filename=/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_15_90sd2s0w_.arc thread=1 sequence=15
archive log filename=/u01/app/oracle/oradata/lonion/redo03.log thread=1 sequence=16
media recovery complete, elapsed time: 00:00:04
Finished recover at 15-AUG-13
RMAN>
But, when I recover database in SQL*Plus command window like below:
[oracle@lonion ~]$ uniread sqlplus /nolog
[uniread] Loaded history (2178 lines)
SQL*Plus: Release 10.2.0.1.0 - Production on Thu Aug 15 19:25:38 2013
Copyright (c) 1982, 2005, Oracle. All rights reserved.
SQL> conn /as sysdba
Connected.
SQL>
SQL> recover database;
ORA-00283: recovery session canceled due to errors
ORA-01610: recovery using the BACKUP CONTROLFILE option must be done
SQL> recover database using backup controlfile;
ORA-00279: change 2147842454 generated at 08/15/2013 18:34:28 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_9_%u_.a
rc
ORA-00280: change 2147842454 for thread 1 is in sequence #9
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
ORA-00279: change 2147842651 generated at 08/15/2013 18:40:25 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_10_%u_.
arc
ORA-00280: change 2147842651 for thread 1 is in sequence #10
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_9_90sd
0slz_.arc' no longer needed for this recovery
ORA-00279: change 2147842653 generated at 08/15/2013 18:40:26 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_11_%u_.
arc
ORA-00280: change 2147842653 for thread 1 is in sequence #11
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_10_90s
d0tsb_.arc' no longer needed for this recovery
ORA-00279: change 2147842656 generated at 08/15/2013 18:40:32 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_12_%u_.
arc
ORA-00280: change 2147842656 for thread 1 is in sequence #12
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_11_90s
d110b_.arc' no longer needed for this recovery
ORA-00279: change 2147842684 generated at 08/15/2013 18:41:21 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_13_%u_.
arc
ORA-00280: change 2147842684 for thread 1 is in sequence #13
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_12_90s
d2ksr_.arc' no longer needed for this recovery
ORA-00279: change 2147842686 generated at 08/15/2013 18:41:23 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_14_%u_.
arc
ORA-00280: change 2147842686 for thread 1 is in sequence #14
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_13_90s
d2mc6_.arc' no longer needed for this recovery
ORA-00279: change 2147842689 generated at 08/15/2013 18:41:27 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_15_%u_.
arc
ORA-00280: change 2147842689 for thread 1 is in sequence #15
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_14_90s
d2qrm_.arc' no longer needed for this recovery
ORA-00279: change 2147842691 generated at 08/15/2013 18:41:28 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_16_%u_.
arc
ORA-00280: change 2147842691 for thread 1 is in sequence #16
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_15_90s
g0or9_.arc' no longer needed for this recovery
ORA-00279: change 2147842986 generated at 08/15/2013 19:14:29 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_17_%u_.
arc
ORA-00280: change 2147842986 for thread 1 is in sequence #17
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_16_90s
g0os5_.arc' no longer needed for this recovery
ORA-00308: cannot open archived log
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_17_%u_
.arc'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
SQL> recover database using backup controlfile;
ORA-00279: change 2147842986 generated at 08/15/2013 19:14:29 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_08_15/o1_mf_1_17_%u_.
arc
ORA-00280: change 2147842986 for thread 1 is in sequence #17
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
/u01/app/oracle/oradata/lonion/redo01.log ---- Yon see, proceeding this process, it can't automatically apply the current redo log.
Log applied.
Media recovery complete.
SQL>
Question Coming:
Now, my question is that 「Why it automatically recover current redo log in RMAN command window but not in SQL*Plus」?
BTW: Please pay attention to the red font.

It also seems not work.
SQL> recover automatic database using backup controlfile;
ORA-00279: change 2148632889 generated at 09/26/2013 12:45:22 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_09_26/o1_mf_1_48_%u_.
arc
ORA-00280: change 2148632889 for thread 1 is in sequence #48
ORA-00278: log file
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_09_26/o1_mf_1_48_%u_
.arc' no longer needed for this recovery
ORA-00308: cannot open archived log
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_09_26/o1_mf_1_48_%u_
.arc'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
ORA-00308: cannot open archived log
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_09_26/o1_mf_1_48_%u_
.arc'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
ORA-00308: cannot open archived log
'/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_09_26/o1_mf_1_48_%u_
.arc'
ORA-27037: unable to obtain file status
Linux Error: 2: No such file
or directory
Additional information: 3
SQL>
It must specify the redo log.
SQL> recover database using backup controlfile;
ORA-00279: change 2148632889 generated at 09/26/2013 12:45:22 needed for thread
1
ORA-00289: suggestion :
/u01/app/oracle/flash_recovery_area/LONION/archivelog/2013_09_26/o1_mf_1_48_%u_.
arc
ORA-00280: change 2148632889 for thread 1 is in sequence #48
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
/u01/app/oracle/oradata/lonion/redo02.log
Log applied.
Media recovery complete.
SQL>

Why Redo log files not backup

Hi everyone,
I have a scenario where the my DB is running in archivelog mode and users are making changes to DB as usual, and all of a sudden my db crashes due to some power outage or failed disks or something bad..
Now my DB is inconsistent i can't access my DB due to a failed disk. I need to perform a complete recovery of the database as the database is in archivelog mode I can restore from a previous backup and apply the redo from the archived logfiles. Here comes my doubt what about the current online redologfile that has not been archived and which contain info about the commited transaction. how to recover the db upto the point of failure. help need in this situation..
Edited by: user8710159 on Feb 14, 2010 1:18 PM

user8710159 wrote:
Hi everyone,
I have a scenario where the my DB is running in archivelog mode and users are making changes to DB as usual, and all of a sudden my db crashes due to some power outage or failed disks or something bad..
Now my DB is inconsistent i can't access my DB due to a failed disk. I need to perform a complete recovery of the database as the database is in archivelog mode I can restore from a previous backup and apply the redo from the archived logfiles. Here comes my doubt what about the current online redologfile that has not been archived and which contain info about the commited transaction. how to recover the db upto the point of failure. help need in this situation..
Edited by: user8710159 on Feb 14, 2010 1:18 PMIf you still had a viable copy of the online redo and current control file, the recover would apply them as well. Without them, you'll have to do an incomplete recovery and reset logs.
Which is why you always want to multiplex your control file and online redo - and have the multiplexed copies as physically separate as possible. Those multiplexed copies are your backup for the online redo logs that have not yet been archived.
Edited by: EdStevens on Feb 14, 2010 5:07 PM

Why the time of the online redo logs doesn't change?

Oracle 11.1.0.7 on windows 2008.I find the time of the online redo logs doesn't change since Jan 18 when I had restarted database,and the time of some datafiles doesn't change either.the database is always online and changes are wrriting to the files, I don't know how this happened?
would anyone help me? thank you.

ROCK wrote:
I found some datafiles have the latest date,but the other not. They all have write/read operations on them.
and the switching of the redo logs doesn't change the timestamps of the logfiles since Jan.18 when I had restarted the database. this situation does not appear on the early 8.1.7 database on windows 2000
Does this situation normal?Hi,
Why dont you post the output of the query you are using such as
select group#, first_time, status from v$log;
select name, last_time, status from v$datafile;
select name, CHECKPOINT_TIME, status from v$datafile_header;Time stamp wont change for offline and may be for temp tablespace.
Regards
Anurag

Best RAID configuration for storing Datafiles and Redo log files

Database version:10gR2
OS version: Solaris
Whis is the best RAID level for storing Datafiles and Redo log files?

Oracle recommends SAME - Stripe And Mirror Everything.
In the RAC Starter Kit documentation, they specifically recommend not using RAID5 for things like voting disk and so on.
SAN vendors otoh claims that their RAID5 implementations are as fast as RAID10. They do have these massive memory caches...
But I would rather err on the safer side. I usually insist on RAID10 - and for those databases that I do not have a vested interest in (other than as a DBA), and owners, developers and management accept RAID5, I put the lead pipe away and do not insist on having it my way. :-)

When occurs crash recovery,why use active online redo log not archived log?

If current redo log had archived, but it's still 'ACTIVE'. As we all know, archived log is just an archived copy of the current redo log which is still 'ACTIVE', they have the same data. But why use active online redo log not archived log for crash recovery?(I think, if crash recovery can use archived log, then whether the online redo log is 'ACTIVE' or not, it can be overwritten)
Quote:
Re: v$log : How redo log file can have a status ACTIVE and be already archived?
Hemant K Chitale
If your instance crashes, Oracle attempts Instance Recovery -- reading from the Online Redo Logs. It doesn't need ArchiveLogs for Instance Recovery.
TanelPoder
Whether the log is already archived or not doesn't matter here, when the instance crashes, Oracle needs some blocks from that redolog. Archivelog is just an archived copy of the redolog, so you could use either the online or achive log for the recovery, it's the same data in there (Oracle reads the log/archivelog file header when it tries to use it for recovery and validates whether it contains the changes (RBA range) in it what it needs).

Aman.... wrote:
John,
Are you sure that the instance recovery (not the media recovery) would be using the archived redo logs? Since the only thing that would be lost is the isntance, there wouldn't be any archived redo log generated from the Current redo log and the previous archived redo logs, would be already checkpointed to the data file, IMHO archived redo logs won't participate in the instance recovery process. Yep, shall watch the video but tomorrow .
Regards
Aman....
That's what I said. Or meant to say. If Oracle used archivelogs for instance recovery, it would not be possible to recover in noarchive log mode. So recovery relies exclusively on the online log.
Sorry I wasted your time, I'll try to be less ambiguous in future

Why not use Redo log for consistent read

Oracle 11.1.0.7:
This might be a stupid question.
As I understand if a select was issued at 7:00 AM and the data that select is going to read has changed at 7:10 AM even then Oracle will return the data that existed at 7:00 AM. And for this Oracle needs the data in Undo segments.
My question is since redo also has past and current information why can't redo logs be used to retreive that information? Why is undo required when redo already has all that information.

user628400 wrote:
Thanks. I get that piece but isn't it the same problem with UNDO? It's written as it expires and there is no guranteee until we specifically ask oracle to gurantee the UNDO retention? I guess I am trying to understand that UNDO was created for effeciency purposes so that there is less performance overhead as compared to reading and writing from redo.And this also you said,
>
If data was changed to 100 to 200 wouldn't both the values be there in redo logs. As I understand:
1. Insert row with value 100 at 7:00 AM and commit. 100 will be writen to redo log
2. update row to 200 at 8:00 AM and commit. 200 will be written to redo log
So in essence 100 and 200 both are there in the redo logs and if select was issued at 7:00 data can be read from redo log too. Please correct me if I am understanding it incorrectly.I guess you didnt understand the explaination that I did. Its not the old data that is kept. Its the changed vector of Undo that is kept which is useful to "recover" it when its gone but not useful as such for a select statement. Whereas in an Undo block, the actual value is kept. You must remember that its still a block only which can contain data just like your normal block which may contain a table like EMP. So its not 100,200 but the change vectors of these things which is useful to recover the transaction based on their SCN numbers and would be read in that order as well. And to read the data from Undo, its quite simple for oracle to do so using an Undo block as the transaction table which holds the entry for the transaction, knows where the old data is kept in the Undo Segment. You may have seen XIDSEQ, XIDUSN, XIDSLOT in the tranaction id which are nothing but the information that where the undo data is kept. And to read it, unlke redo, undo plays a good role.
About the expiry of Undo, you must know that only INACTIVE Undo extents are marked for expiry. The Active Extents which are having an ongoing tranaction records, are never marked for it. You can come back after a lifetime and if undo is there, your old data would be kept safe by oracle since its useful for the multiversioning. Undo Retention is to keep the old data after commit, something which you need not to do if you are on 11g and using Total Recall feature!
HTH
Aman....

Redo Log Members & RAID 5

Hi,
My production database servers run on HP-XP storage, raid 5. Currently the redo logs are striped on 16 disks, as raw files. I use 5 groups, 2 members in each group.
I wanted to hear your opinion, if two members are still necessary with todays storage hardware, considering the mirroring already done in the hardware level.
What is the benefit today for having more than one member in a group, and do you think it's worth the IO price most of us are still paying...
Thanks in advance,
Idan.

For example here:
http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:359617936136
Try search google btw. There are plenty of articles.
Just if you read concepts of RAID you will learn that RAID 5 is not good for write intensive operations (redo logs are write intensive).

Why multiplex redo log group ?

Hello,
Why should we multiplex redo log groups if we have only file system which is already mirrored. Is there any one who had an incident when he has only one redo log member per group placed on a mirrored file system but still got corrupted and he felt better to have multiple members even if they reside on the same file system (which is mirrored)
Thanks
Salman

Ansiktet wrote:
EdStevens wrote:
Salman Qureshi wrote:
Hello,
Why should we multiplex redo log groups if we have only file system which is already mirrored. Is there any one who had an incident when he has only one redo log member per group placed on a mirrored file system but still got corrupted and he felt better to have multiple members even if they reside on the same file system (which is mirrored)
Thanks
SalmanThe mirror won't protect you from an SA who deletes '/u01/oradata/redo01.log' because he is running out of space on /u01 and figures its safe to delete a log file.
Or similar types of errors.
The redo and control files are simply too critical to put all your eggs in one basket when planning their protection.:) Thats why you should not use Oracle default .log on redo, instead .dbf or .dbl can be used. THat's why I use the older (pre-10g) default of .rdo for redo logs
However, has this happend anyone for real, that a SA delete Oracle files? Where do you think I came up with the example?
HOw about an SA (or maybe the kind of "fresher" we often see here, Taking a look at a "log" file with notepad?
If he is isnt stupid he should know that Oracle resides on /u01 partion (for example), and should not delete files there without consulting the DBA."should" is the operative word there. There is no accounting for corporate cultures and attitudes.
But end the end, my example was to illustrate that not all problems with redo and control files are mitigated with disk mirroring.

Where RFS exactly write redo data ? ( archived redo log or standby redo log ) ?

Good Morning to all ;
I am getting bit confused from oracle official link . REF_LINK : Log Apply Services
Redo data transmitted from the primary database is received by the RFS on the standby system ,
where the RFS process writes the redo data to either archived redo log files or standby redo log files.
In standby site , does rfs write redo data in any one file or both ?
Thanks in advance ..

Hi GTS,
GTS (DBA) wrote:
Primary & standby log file size should be same - this is okay.
1) what are trying to disclose about largest & smallest here ? - You are confusing.
Read: http://docs.oracle.com/cd/E11882_01/server.112/e25608/log_transport.htm#SBYDB4752
"Each standby redo log file must be at least as large as the largest redo log file in the redo log of the redo source database. For administrative ease, Oracle recommends that all redo log files in the redo log at the redo source database and the standby redo log at a redo transport destination be of the same size."
GTS (DBA) wrote:
2) what abt group members ? should be same as primary or need to add some members additionally. ?
Data Guard best practice for performance, is to create one member per each group in standby DB. on standby DB, one member per group is reasonable enough. why? to avoid write penalty; writing to more than one log files at the standby DB.
SCENARIO 1: if in your source primary DB you have 2 log member per group, in standby DB you can have 1 member per group, additionally create an extra group.
primary
standby
Member per group
2
1
Number of log group
4
5
SCENARIO 2: you can also have this scenario 2 but i will not encourage it
primary
standby
Member per group
2
2
Number of log group
4
5
GTS (DBA) wrote:
All standby redo logs of the correct size have not yet been archived.
- at this situation , can we force on standby site ? any possibilities ?
you can not force it , just size your standby redo files correctly and make sure you don not have network failure that will cause redo gap.
hope there is clarity now
Tobi

RAID level for Redo

Hi,
My storage admin created RAID10 and RAID5 for database, I would like to know which RAID Level is best for keeping the REDO logs. Can someone tell me what's best for REDO?
Thanks

hello,
In case of using redo logs then you need performance and availability.that is why i put this comparison for you.
I suggest you use raid 5 because it is faster in the write operations and more recoverable.*
<pre class="jive-pre">Note: RAID 5 disks are primarily used in the processes that require transactions. Relational databases are among the other fields that run very well under a RAID 5 storage scheme*</pre>
RAID 5 vs RAID10
Data Loss and Data Recovery
Let us start off by having RAID 5 explained. In RAID 5, the data backup of any one of the disks is created. If there are 5 disks, in the storage system, then 4 of the disks will be used for storing the data and one of the disks will be used for keeping the backup of any one of the hard disks. If one of the disks in the array fails, then the data can be recovered, but in the event of a second disk failure, the recovery is not possible. RAID 10 on the other hand is a combination of RAID 0 and RAID 1. In a RAID 10 storage scheme, an even number of disks is required. Each disk array has a disk array, which is a mirrored set of the former. In RAID 10, data recovery of all but one disk can be performed. In the case of a disk failure, all the remaining disks can be used effectively without any impact on the storage scheme.
Performance
The RAID 5 performance in the read operations is quite appreciated, though its write operation is quite slow, as compared to RAID 10. RAID 10 is thus used for systems which require high write performance. Hence, it is very obvious, RAID 10 is not used for systems like heavy databases, which require high speed write performance.
Redundancy
The RAID 10 arrays are more data redundant than the RAID 5 arrays. This makes RAID 10 an ideal option for the cases where high data redundancy is required.
Architectural Flexibility
RAID 10 provides more architectural flexibility, as compared to RAID 5. The amount of free space left is also minimized, if you use a RAID 10 data storage scheme.
Controller Requirement
RAID 5 demands a high end card for the data storage performance. If the purpose of the RAID 5 controller is being solved by the operating system, then it will result in the slowing down of the performance of the computer. In case of a RAID 10 controller, any hardware controller can be used.
Applications
RAID 10 finds a wide variety of applications. Systems with RAID 0, RAID 1 or RAID 5 storage schemes are often replaced with a RAID 10 storage scheme. They are mainly used for medium sized databases. RAID 5 disks are primarily used in the processes that require transactions. Relational databases are among the other fields that run very well under a RAID 5 storage scheme.
With this, I complete the RAID 5 vs RAID 10 comparison. This comparison, I hope, will help you in deciding the right storage scheme, that can suit your purpose.
kind regards
Mohamed

Disk array configurations with oracle redo logs and flash recovery area.

Dear Oracle users,
We are planning to buy the new server for oracle database 10g standard edition. We put oracle database file, redo logs, and flash recovery area on each of disk array. My question is what is the best disk array configuration for redo logs and flash recovery area? RAID 10 or RAID 1? Is that possible we can duplicate Flash recovery area to the other location (such as net work drive) at the same time? Since we only have single disk array controller to connect to the disk arrays, I am try to avoid the single failure that will lose archive logs and daily backup.
thanks,
Belinda

Thank you so much for the suggestion. Could you please let me know the answer for my question of FRA redundancy?
“Is that possible we can duplicate Flash recovery area to the other location (such as net work drive) at the same time? Since we only have single disk array controller to connect to the disk arrays, I am try to avoid the single failure that will lose archive logs and daily backup.”

Redo Log - Storage Consideration

I have one question about redo Log storage guidelines, that i red in one article on metalink
In that article recommended place redo log on raid device level 1 (*Mirroring*),
and NOT recommended place it on raid 10 or 5
If you know - explain detailed please, why it is so?
Scientia potentia est

I haven't seen a raid 0, raid 1, or raid 5 filesystem in the last 5 years. Most companies now use SAN or NAS.
That is not entirely true is it Robert. Most default SAN installation are set up as Raid5 and are presented to the users as filesystem mounts.
I agree entirely re the benefits of using ASM
The reason why redo logs are recommended to be on Raid1 (1+0, 10) and not Raid5 is that redo logs write differently to all other oracle datafiles as they are written sequentially by the LGWR process. Raid5 involves writing parity data to another disk and therefore adds additional writes to what can already be a very intensive single-streamed process
John
www.jhdba.wordpress.com

Avoid RAID-5 on Redo Logs- WHY?

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