ASM Rebalancing ?

Hi,
I'm about to add a new disk/diskgroup into an existing ASM group informing Oracle not to rebalance it now. I'm planning to rebalance manually later on.
What would happend if a new files gets created in the newly added disk/diskgroup where rebalancing is not applied?
Would Oracle perform rebalance automatically when a new file gets created?
Need your suggestions please?
Thanks,
Kam

By default Oracle will start rebalancing a diskgroup the moment a new disk/lun is added. To prevent this (in 10gR2 and 11gR1) you can set the asm_power_limit to 0:
SQL> alter system set asm_power_limit=0;
This will stop all rebalancing actions until you want to do it, by default it is set to 1 with a range of 0-11. As long as asm_power_limit=0, no parts of any datafile (or other file) in asm will spread to the new disk. When you are ready, you can set the asm_power_limit to 1-11 to start the rebalance.
Node: In 10gR1 you can only set the power limit to 1, it cannot be stopped, so this option would be off the table.
Cheers
Jay Caviness
http://www.grumpy-dba.com

Similar Messages

Oracle ASM rebalancing does change rowid??

Hi, all.
The db is 11.2.0.3 on a linux machine.
I use ASM for storage management.
When oracle ASM rebalancing occurs, does the rowid of rows change?
In my production environment, some application modules depend on rowid of rows.
Have a wonderful day.
Best Regards.

Hi
When oracle ASM rebalancing occurs, does the rowid of rows change?No, the load balancing is doie by moving ASM allocation units i.e datafiles extents (synonymous to OS blocks) to other physical volumns within same diskgroup to make data spread across all volumes in a balanced way. It has nothing to do with rowids and you should not worry about it.
Salman

ASM, rebalancing, 3rd party storage and performance

Hi all, I have some questions for the storage experts and I need your opinion about:
1. Which type of ASM is better for the rebalancing perspective (and obviously the performance perspective), but considering the availability as well: Unprotected, 2-way (normal) or 3-way (high)? I know 3-way is the worst because we have to multiply by 3 the space of the database, but has great availability. Which of these do you use in your company?
2. If someone is using EMC/Fujitsu/Hitachi, do you use Unprotected or 2-way (normal) in ASM?
3. Which type of rebalancing (from zero to 11) is the best to use, considering the overall performance , I mean, when you have to add a new disk, ASm will perform the rebalancing.
4. Which is better to use: ASM Cluster File System or Oracle Cluster File System ?
Thanks.

977623 wrote:
1. Which type of ASM is better for the rebalancing perspective (and obviously the performance perspective), but considering the availability as well: Unprotected, 2-way (normal) or 3-way (high)? I know 3-way is the worst because we have to multiply by 3 the space of the database, but has great availability. Which of these do you use in your company?Wrong question IMO. You do not choose normal or high redundancy based on which rebalances the fastest. You make that choice wrt to redundancy and high availability.
The best in this respect is high redundancy. 3 storage servers. Fully redundant I/O fabric layer (3+ I/O paths from each server to each and every LUN). Which means you can loose 2 storage arrays and most of your I/O fabric layer (switches and cables). And the storage layer left will still be able to be effectively used for ASM and the RAC database will not even notice that this destruction happened.
However, this best is not always feasible ito existing architecture, budget and so on. So that drives the requirements and needs and what the best is to meet that.
2. If someone is using EMC/Fujitsu/Hitachi, do you use Unprotected or 2-way (normal) in ASM?That again depends on redundancy levels. If the SAN provides a RAID5 or RAID10 LUN, should you mirror it?
This may makes sense if you have 2 SANS. And with each SAN implementing RAID5, you mirror (via ASM) across SANs.
It makes less sense if you use ASM to mirror (on the same SAN) 2 RAID5 LUNs.
You also may have no choice. For example, migrating a high redundancy diskgroup from a storage server (no redundancy by server), to a SAN (RAID5/10 redundancy by SAN). When migrating ASM diskgroups, you cannot reduce redundancy. You cannot make a high redundancy diskgroup a normal redundancy diskgroup. Or a normal one, an externally redundant diskgroup.
In such a case you normal/high redundancy diskgroup on the new SAN (with its RAID5/10 LUNs), still need its own mirrors in ASM.
3. Which type of rebalancing (from zero to 11) is the best to use, considering the overall performance , I mean, when you have to add a new disk, ASm will perform the rebalancing.How busy is the I/O layer? What production processing is running? How will this be impacted by using power 11? How soon does the old (dropped) disks need to be physically decommissioned? Etc.
There is no single correct answer to what load balancing power setting to use.
4. Which is better to use: ASM Cluster File System or Oracle Cluster File System ?For what purpose?
For RAC database purposes only? ACFS. As OCFS adds another set of kernel drivers, kernel services, and another Interconnect (ocfs needs its own IP Interconnect that is typically run over the public IP network of the cluster, and that can be/should be run over the private IP network of the cluster).
Why add more moving parts (ocfs) when ACFS is available?
Then again - why use ACFS when you are not running Grid Infrastructure? Or why makes your cluster file system dependent on Grid/CRS to be running (with ASM), when OCFS's moving parts are significantly fewer and less complex?
As with most things in Information Technology - there is no overall "best". The "best" depends on a number of factors, and the business requirements that need to be met.

Stop running asm rebalancing proecss

Hi,
I'm working on an Oracle Database 11g Release 11.1.0.6.0 - 64bit Production With the Real Application Clusters option.
I added a new disk to a diskgroup, and the rebalacing process started.
Is it possible to stop it, and re-run later manually?
If it's possible, there are some bad side effects of this operation?
Thanks in advance,
Samuel

No this is not possible.
You should have waited adding the disk until it was more convenient, or manually set the rebalance power to e.g. a value of 1 ( one ), so it is not very resource consuming
HTH
FJFranken

ASM Rebalance Power

Hi, there,
This is probably a stupid question. I think most of mine are...!
For ASM rebalancing, if we don't specify a POWER value in our ALTER DISKGROUP data REBALANCE statement, it defaults to whatever the value of asm_power_limit is. On our system, this is 4
However, whenever we had to drop a disk from our Exadata machine, we specified the REBALANCE POWER of 11 for the DATA diskgroup to speed things up (we had to…). We left the other two diskgroups at 4 because they were hardly used at the time.
Whenever we replaced the disk in the array, the storage cell picked it up and performed a rebalance. Again, the DATA diskgroup ran at a rebalance power of 11 and the other ran at 4 (the default).
Is there a setting somewhere which overrides the ASM instance’s default (asm_power_limit) for individual diskgroups. I’m worried now that all ASM rebalance operations on that diskgroup will be running at power 11 and causing performance hits to my system…
I’ve tried reading the fine manuals and it seems like the only option is to perform the rebalance itself:
ALTER DISKGROUP data REBALANCE POWER 4;
Not great as I don’t want to kick off a rebalance if I can help it…
Mark

Apparently, the REBALANCE POWER for a diskgroup is the last POWER granted by either a 'ALTER DISKGROUP ... REBALANCE POWER x' statement or by a reading of the spfile. In our case, the REBALANCE POWER for the diskgroup is 11.
In order to reduce this down to the default REBALANCE POWER (asm_power_limit), we have to either make ASM read the SPFILE (either dismount/mount the diskgroup or restart ASM) or we have to issue a new statement. This statement will perform a REBALANCE:
ALTER DISKGROUP data REBALANCE POWER 4;
Hope this helps someone out in the future!

Can one tablepace have their datafile on ASM also filesystem. ???

Hello Oracle Gurus''
1.can one tablespace have their datafile on ASM as well as filesystem ?? like 1 tablespace =1ASMfile + 1 localfilesystem file
2.also tell me will there be any database error code triggered on the DB alert log file. if we use the datafiles on ASM as well as local filesystem for one tablespace??and any performance issues on that tablespaces which resides on filesystem and ASM disk both? ..if all are fine how the filesystem datafile will be support for ASM rebalancing also mirroring level on ASM ??
3.what is type of SCN? is there any types we have ?
4.what are the wait events views on RAC clusters used? to monitor the cluster events and rectify the issues?

user13014926 wrote:
Hello Oracle Gurus''
1.can one tablespace have their datafile on ASM as well as filesystem ?? like 1 tablespace =1ASMfile + 1 localfilesystem file
Yes.
2.also tell me will there be any database error code triggered on the DB alert log file. if we use the datafiles on ASM as well as local filesystem for one tablespace??and any performance issues on that tablespaces which resides on filesystem and ASM disk both? ..if all are fine how the filesystem datafile will be support for ASM rebalancing also mirroring level on ASM ??
AFAIK no. The files which are present on the disk/file system only and not on asm, are not managed by it so no support for asm based striping and mirroring would be there for them.Second, rebalancing is NOT done for the files but for the disks when they are not present or have become offline due to some reason.
3.what is type of SCN? is there any types we have ?
Just remember one type, System Commit Number and forget about rest.
4.what are the wait events views on RAC clusters used? to monitor the cluster events and rectify the issues?Please see the Performance Tuning section of Oracle RAC Admninistration guide with a special attention to Cluster wait class and wait events related to it. Best is, use EM and it would show all the things in a nice manner.
HTH
Aman....

Benefit of rebalance

Hi folks,
what are benefit of rebalance in ASM?
thanks & regards.

Hi,
ASM Rebalancing >>>>>>>>>>>>>>>>>>>>>>>
    "Rebalancing" is the process of moving file extents onto or off of disks for the purpose of evenly distributing the I/O load of the diskgroup
    It occurs asynchronously in the background and can be monitored
    In a clustered environment, rebalancing for a disk group is done within a single ASM instance only and cannot be distributed across multiple cluster node to speed it up
    ASM will automatically rebalance data on disks when disks are added or removed
    The speed and effort placed on rebalancing can be controlled via a POWER LIMIT setting
    POWER LIMIT controls the number of background processes involved in the rebalancing effort and is limited to 11. Level 0 means no rebalancing will occur
    I/O performance is impacted during rebalancing, but the amount of impact varies on which disks are being rebalanced and how much they are part of the I/O workload. The default power limit was chosen so as not to impact application performance
Thanks,
Rajasekhar

ASM Disk Rebalancing

How will you Rebalance ASM Diskgroup?
DBA needs to do it or its a manual Procees?

Rangaraj wrote:
How will you Rebalance ASM Diskgroup?
DBA needs to do it or its a manual Procees?Its done automatically by ASM's RBAL process which would initiate the slaves ARB's to do so. Its an automatic process and doesn't need manual intervention in general. If you still want to do it, you can do so with the alter diskgroup command.
http://download.oracle.com/docs/cd/E11882_01/server.112/e10500/asmdiskgrps.htm#OSTMG10080
HTH
Aman....

Looking for information on the below questions on ASM

Scenario: (Oracle 10g on Windows 2003 with EMC storage)
ASM Partition table crashed for LUN 20 on 18th July
DB was up and running till 23rd July (New LUN (LUN 36) was presented and the RMAN backup used to restore the data that were residing on the corrupt LUN)
End of the day everything screwed up and the complete grid (4 nodes) was rebuild.
Links:
As mentioned in the link: http://www.exforsys.com/forum/oracle-database/487-what-asm-instance-oracle.html
"The ASM instance is only involved during the creation or deletion of files and when disk configurations change (such as dropping or adding a disk). When these types
of changes occur, the ASM instance automatically rebalanced the disks and provides the necessary information to refresh the extent map in the SGA of the database
instance. Of course, this process requires that the ASM instance run concurrently with the database instance, and only shut down after the database instance is
closed."
As mentioned in the link: http://www.orafaq.com/wiki/ASM_FAQ#ASM_disk_header.2Fsuperblock_backups.3F
"ASM disk headers (super-blocks) cannot be backed up and restored in Oracle 10g. By implication, if you use EXTERNAL REDUNDANCY and a single disk's header is
accidentally overwritten, the entire disk group will have to be restored."
As mentioned in the link: http://www.datadisk.co.uk/html_docs/oracle/asm.htm
"ASM is a special instance that does not have any data files, there is only ASM instance one per server which manages all ASM files for each database. The instance
looks after the disk groups and allows access to the ASM files. Databases access the files directly but uses the ASM instance to locate them. If the ASM instance is
shutdown then the database will either be automatically shutdown or crash. "
With the above scenario and the documents provided in the links above, I am unable to get the complete picture of what went wrong. Will be great if some one could
through more light on the below questions. (Note: we have multiple vendor engaged managing different part of this outage and unable to get the real fact of what went
wrong)
1, The ASM had given the details of the disk to the DB, and the DB is managing the disk directly. Also the DB and the ASM instance were up and running till 23rd is
what i understand going by the details given in the above links, in this scenario how can we confirm that the partition table is corrupt / missing. Is their a way to
check the same?
2, ASM disk headers (super-blocks) cannot be backed up, that means that it can not be read directly. Then is it possible to say that the ASM disk header is corrupt /
missing?
3, If the ASM disk header / partition table of LUN 20 is corrupt on 18th, can the DB run till 23rd without any issue? will the ASM & DB does not crash?
4, ASM will strip the data across the available LUN's, will it not be able to rebuild the data on the newly presented LUN 36 instead of using RMAN backup to rebuild the
data? or is the ASM not configured as it should be done. (WE have multiple LUN's presented to this Grid)
Edited by: 880333 on Aug 19, 2011 12:35 AM

What relation with the Oracle Forms product ?
Francois

Advantages of using ASM

Can someone tell me some reason for using
ASM when using hardware stripe & mirror
besides that files are created and managed automatically?

Hi,
In large-scale environments, ASM eases the task of managing thousands of database files by using DISK GROUPS instead. Disk Groups are disk devices managed as a logical unit. When creating a new tablespace, control file, or redo log file you can specify a disk group as the storage area for the database structure rather than an operating system file.
ASM uses OMF and mirroring and striping features to provide a file system and logical manager that supports multiple databases, nodes, and RAC. ASM eliminates the need to purchase a 3rd party logical volume manager... ASM strips files, not logical volumes.
In addition to spreading db objects over multiple devices, ASM allows new disk devices to be added to the database while the database is running, as well as automatically rebalancing the distribution of files w/ minimum intervention.
The DBA assumes the traditional role of "System-admin space manager" this brings hardware provisioning for db objects more closely into the world of the DBA.
Can someone tell me some reason for using
ASM when using hardware stripe & mirror
besides that files are created and managed
automatically?

How to add and remove storage from ASM at the same time?

Scenario:
I want to drop some disks from asm
1- Add disk to asm -----> rebalance
2- drop disk from asm ----> rebalance
Is there anyway to make this process faster instead of going to rebalancing twice?

I think you could try something like this.....
Add with a power limit of zero and then drop the disks with a powerlimit of 11.
alter system set ASM_POWER_LIMIT=0;
select * from v$asm_operation;
alter diskgroup DBFILE01_GRP
add disk 'ORCL:DB0009', 'ORCL:DB0010', 'ORCL:DB0011', 'ORCL:DB0012';
alter diskgroup DBFILE01_GRP drop disk DB0001, DB0002, DB0003, DB0004;
alter diskgroup DBFILE01_GRP rebalance power 11;
select * from v$asm_operation;

Which is better ASM or file system storage

Hi all, I need a urgent help from all u gr8 DBAs.
I have to give justification to my client that which is better to use between file based option ASM and why??
So can anyone give me some write up in this line?

Ok, how about this
Today's large databases demand minimal scheduled downtime, and DBAs are often required to manage multiple databases with an increasing number of database files. Automatic Storage Management lets you be more productive by making some manual storage management tasks obsolete.
The Oracle Database provides a simplified management interface for storage resources. Automatic Storage Management eliminates the need for manual I/O performance tuning. It simplifies storage to a set of disk groups and provides redundancy options to enable a high level of protection. Automatic Storage Management facilitates non-intrusive storage allocations and provides automatic rebalancing. It spreads database files across all available storage to optimize performance and resource utilization. It also saves time by automating manual storage tasks, which thereby increases their ability to manage more and larger databases with increased efficiency. Different versions of the database can interoperate with different versions of Automatic Storage Management. That is, any combination of release 10.1.x.y and 10.2.x.y for either the Automatic Storage Management instance or the database instance interoperate transparently.
http://download-east.oracle.com/docs/cd/B19306_01/server.102/b14220/mgmt_db.htm

Asm and node shutdown

Hi,
Due to maintenance of our IT infrastructure we need to perform a clean shutdown one of our 2-node RAC.
This maintenance during about one week.
What is the correct procedure to shutdown node,asm e diskgroup of this node?
After the startup the diskgroup rebalanced automatlically?
thanks

You can refer below link as well
Oracle DBA and RAC DBA Expert: How to STOP and START processes in Oracle RAC and Log Directory Structure
Regards,
http://www.oracleracexpert.com
Thread 1 cannot allocate new log & Checkpoint not complete
Move Datafile between DikGroups in ASM

ASM Disk Remove/Add Question

Hello All,
I have a quick question -
We have an ASM Diskgroup that had 8 Disks in it. I removed 2 Diskss and the Diskgroup has been rebalanced. I have not done anything with the removed Disks.
They both appear in the ASM target as eligble to add back into the Diskgroup.
Do I need to re-format/partition/create disk on them before adding them back in? Would existing data on the Diskl cause an issue in the Diskgroup?
This is the first time I will be adding back Disks that have been previously in the Diskgroup.
Thanks in advance for the advice.
Michele

Hi,
Disks eligible to be assigned to a diskgroup must have the status "CANDIDATE" or "FORMER" or "PROVISIONED".
· CANDIDATE - Disk is not part of a disk group and may be added to a disk group with the ALTER DISKGROUP statement
· PROVISIONED - Disk is not part of a disk group and may be added to a disk group with the ALTER DISKGROUP statement. The PROVISIONED header status is different from the
CANDIDATE header status in that PROVISIONED implies that an additional platform-specific action has been taken by an administrator to make the disk available for ASM.
· FORMER - Disk was once part of a disk group but has been dropped cleanly from the group. It may be added to a new disk group with the ALTER DISKGROUP statement.
The ALTER DISKGROUP...DROP DISK without WAIT option statement returns before the drop and rebalance operations are complete. Do not reuse, remove, or disconnect the dropped disk until the HEADER_STATUS column for this disk in the V$ASM_DISK view changes to FORMER.
You don't need change anything on OS Level. Oracle will reuse asmdisk dropped without needs perform any administrative task on OS Level.
Regards,
Levi Pereira

ASM 11.1.0.7.0 and RDBMS client with version (10.2.0.4)

Hi all,
we are trying to expand the space in our ASM. Using a RAC system with two instances.
- ASM Version is 11.1.0.7.0
- RDBMS client with version (10.2.0.4)
Ad the time the ASM is rebalancing the database instances are going down.
- The alert logs from ASM
SQL> ALTER DISKGROUP ORADATA ADD DISK '/dev/mapper/1HITACHI_D60062610068-part1' SIZE 51199 M REBALANCE POWER 2
WARNING: Deprecated privilege SYSDBA for command 'ALTER DISKGROUP ADD/DROP/REBALANCE'
NOTE: Assigning number (2,2) to disk (/dev/mapper/1HITACHI_D60062610068-part1)
NOTE: requesting all-instance membership refresh for group=2
NOTE: initializing header on grp 2 disk ORADATA_0002
NOTE: cache opening disk 2 of grp 2: ORADATA_0002 path:/dev/mapper/1HITACHI_D60062610068-part1
NOTE: requesting all-instance disk validation for group=2
Tue Oct 13 15:12:42 2009
NOTE: disk validation pending for group 2/0x44480376 (ORADATA)
Tue Oct 13 15:12:45 2009
Tue Oct 13 15:12:45 2009
WARNING: RDBMS client (SID1:SID,ÿ) with version (10.2.0.4.0) is not compatible with a pending operation
NOTE: ASM client SID1:SID died unexpectedly.
Alert Logs from DB Instance
ORA-15064: error in comunication with ASM-Instance..
Shutting down instance
My question: Does anyone know if we face a bug ore some configuration issues ?
THX ! Woo

Hy Moo,
My question: Does anyone know if we face a bug ore some configuration issues ?It seems to be some kind of problem in the disk group configuration. You can verify it querying compatibility and database_compatibility fields from v$asm_diskgroup view.
As You should know, there are ASM new features that requires COMPATIBLE.ASM and COMPATIBLE.RDBMS attributes of the ASM diskgroup be set to at least Oracle 11.1. ( Fast Disk Resync is one example of it), maybe You are facing a configuration issue, not hitting a bug.
Hope it helps,
Cerreia

ASM Rebalancing ?

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