Asm Enhancements

8/13/2019 Asm Enhancements

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ASM 11g R1/R2 Enhancements

Suresh Gandhi


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Agenda

} R1 Enhancements New Disk Group Compatibility Attributes

Fast Mirror Resync

Rolling Upgrade

SYSASM Privilege and OSASM OS Group

Scalability and Performance Enhancements

New ASMCMD Commands and Options

Preferred Read Failure Groups

Fast Rebalance

Miscellaneous Disk Group Maintenance Enhancements

} R2 Enhancements ASM Cluster File System (ACFS)

ASM Dynamic Volume Manager (ADVM)

ASM FS Snapshot

Oracle Cluster registry OCR and Voting Disk on ASM

ASM Intelligent Data Placement

ASM Storage Management Configuration Assitant

ASM File Access Control

} Some Practices on new Database Home on ACFS Filesystem

Invoking ASMCMD Commands for volume management


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ASM How it works

ServerRDBMS ASM

Disk Group

Create File

Allocatio

n

File

I/O

Extent Map

OS / ADVM

- File Layout Info

- Update Statistics

- Health Info

Database File Open

ASM Manages Metadata

Not in I/O Path

RAW Performance

Disk Group


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Some Important Notes on ASM:} Oracle ASM Storage Limits

Oracle ASM provides near unlimited capacity for future growth, but does have some storage limits.

For example, Oracle ASM has the following limits on the number of disk groups, disks, and files:} 63 disk groups in a storage system} 10,000 Oracle ASM disks in a storage system} 1 million files for each disk group

} Without any Oracle Exadata Storage, Oracle ASM has these storage limits:} 2 terabytes (TB) maximum storage for each Oracle ASM disk} 20 petabytes (PB) maximum for the storage system

} With all Oracle Exadata Storage, Oracle ASM has these storage limits:

} 4 PB maximum storage for each Oracle ASM disk} 40 exabytes (EB) maximum for the storage system

} The maximum size limit of a disk group equals the maximum disk size multiplied by the maximum numberof disks in a disk group (10,000).

} File size limits are dependent on the value of the disk group compatibility attributes. Oracle ASM supportsfile sizes greater than 128 TB in any redundancy mode when the COMPATIBLE.RDBMS disk groupattribute is set greater than10.1.

} If COMPATIBLE.RDBMS is set to 10.1, the file size limits are less. For example, withCOMPATIBLE.RDBMS equal to 10.1 and the AU size equal to 1 MB, Oracle ASM file size limits are:

} External redundancy: 35 TB} Normal redundancy: 5.8 TB

High redundancy: 3.9 TB


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R1 New Disk Group Compatibility Attributes} Oracle 11g ASM includes two new compatibility attributes that determine the version of

the ASM and database software that can use specific disk groups:

} COMPATIBLE.ASM - The minimum version of the ASM software that can access the disk group. In 11g, thedefault setting is 10.1.

} COMPATIBLE.RDBMS - The minimum COMPATIBLE database initialization parameter setting for any database instancethat uses the disk group. In 11g, the default setting is 10.1.

} SQL> CREATE DISKGROUP data DISK '/dev/raw/*' ATTRIBUTE 'compatible.asm' = '11.1';

} SQL> CREATE DISKGROUP data DISK '/dev/raw/*' ATTRIBUTE 'compatible.rdbms' = '11.1', 'compatible.asm' ='11.1';

Note:- The compatibility versions of a disk group can only be increased, not decreased. If you have increased the version by mistake, you will need tocreate a new disk group.

} SELECT group_number, name, compatibility, database_compatibility FROM

v$asm_diskgroup;

GROUP_NUM# NAME COMPATIBILITY DATABASE_COMPATIBILI------------ ---------- -------------------- --------------------

1 DATA 11.1.0.0.0 11.1.0.0.0


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R1 - Fast Mirror Resync

} During transient disk failures within a failure group, ASM keeps trackof the changed extents that need to be applied to the offline disk.Once the disk is available, only the changed extents are written toresynchronize the disk, rather than overwriting the contents of theentire disk. This can speed up the resynchronization process

considerably.

}Applicable only when Disk Compatable Attribute set to 11.1.0 orhigher

} Default time to repair the disk is 3.6 hrs determine by

DISK_REPAIR_TIME attribute} Can override by using Alter disk offline disk clause.


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R1 - Scalability and Performance Enhancements

}ASM files are stored in a disk group as a collection of extents} Oracle 10g each extent mapped directly to one allocation unit (AU)

} In 11G, an extent can be made up of one or more allocation units

As files get larger, the extent size can grow to reduce the size of theextent map describing the file

When the disk group compatibility attributes are set to 11.1 or higher,} The first 20,000 extents match the allocation unit size (1*AU)

} The next 20,000 extents are made up of 8 allocation units (8*AU).

} Beyond that point, the extent size becomes 64 allocation units (64*AU).

}Also controls or enhances the AU size by specifying 'au_size' disk

attribute} CREATE DISKGROUP disk_group_2 EXTERNAL REDUNDANCY DISK

'/dev/sde1' ATRRIBUTE 'au_size' = '32M';

} Values can be ranging from 1M to 64M


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R1 - Preferred Read Failure Groups

} In Oracle 10g, ASM always reads the primary copy of the mirroredextent set.

} This isn't a problem when both nodes and both failure groups are alllocated in the same site, but it can be inefficient for extendedclusters, causing needless network traffic.

} Oracle 11g allows each node to define a preferred failure group,allowing nodes in extended clusters to access local failure groups inpreference to remote ones

} Instance Level ParameterASM_PREFERRED_READ_FAILURE_GROUPSmust be set for each node

Example:-SQL>ALTER SYSTEM SET ASM_PREFERRED_READ_FAILURE_GROUPS =

'data.data_0000', 'data.data_0001', 'data.data_0002';


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R1 - Fast Rebalance} The "ALTER DISKGROUP ... MOUNT" statement allows disk groups to be mounted in restricted

mode.

} Using RESTRICTED mode improves the performance of rebalance operations in a RACenvironment as it elimitates the need for lock and unlock extent map messaging that occursbetween ASM instances

SQL> SELECT name FROM v$asm_diskgroup;

NAME------------------------------DATA

SQL> ALTER DISKGROUP data DISMOUNT;

Diskgroup altered.

SQL> ALTER DISKGROUP data MOUNT RESTRICTED;

Diskgroup altered.

SQL> ALTER DISKGROUP data DISMOUNT;

Diskgroup altered.

SQL> ALTER DISKGROUP data MOUNT;

Diskgroup altered.


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R1 - Disk Group Maintenance Enhancements} The CHECK clause of the ALTER DISKGROUP command has been simplified so there are only

two options, NOREPAIR and REPAIR, available, with NOREPAIR as the default. Summarizederrors are displayed, with full error messages writen to the alert log. ALTER DISKGROUP data CHECK; -- Like NOREPAIR ALTER DISKGROUP data CHECK NOREPAIR; ALTER DISKGROUP data CHECK REPAIR;

} The ALTER DISKGOUP command now includes ONLINE and OFFLINE clauses so disks can betaken offline for repair before being brought back online. -- Individual disks.

} ALTER DISKGROUP data OFFLINE DISK 'disk_0000', 'disk_0001';} ALTER DISKGROUP data ONLINE DISK 'disk_0000', 'disk_0001';

-- Failure groups.} ALTER DISKGROUP data OFFLINE DISKS IN FAILGROUP 'fg_0000';} ALTER DISKGROUP data ONLINE DISKS IN FAILGROUP 'fg_0000';

-- Bring online all disks in disk group.} ALTER DISKGROUP data ONLINE ALL;

} Disk groups that can't be mounted by ASM can now be dropped using the FORCE keyword of theDROP DISKGROUP command.

} DROP DISKGROUP data FORCE;


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R1-ASMCMD new commands

} Md_backup:-} MD_Restore

} CP

} Startup

} remap


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R2 ASM Cluster File System

} a robust, modern, general purpose file system for files beyond theOracle database files.

}ACFS provides support for files such as Oracle binaries, report files,trace files, alert logs, and other application data files.

}ACFS is highly available leveraging the ASM mirroring and striping

features in addition to hardware Redundant Array of InexpensiveDisks (RAID) functionality.

}ACFS supports large files with 64-bit file and file system datastructure sizes leading to exabyte-capable file and file systemcapacities


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R2 ASM Snapshots} ASM FS Snapshot is a point-in-time copy of a file system and can provide up to 64

snapshot images. ASM FS Snapshot performs fast creation of persistent ASM FSimages at a specific point-in-time with low overhead leveraging the Copy on Writetechnology.

} Read-only ASM FS Snapshots can be generated on an interval basis. They may residein existing ASM FS storage or in an additional storage device and persist following asystem restart.

} Even as the file system changes, the snapshot does not, giving you the ability to viewthe file system as it was at the time the snapshot was created. Initially, snapshots areread-only, which preserves their point-in-time capture. The following are the benefits of

ASM FS Snapshots: ASM FS Snapshots can be used as a source for backup. The original file system can continue

to change but the static nature of the snapshot makes them ideal as a source for backupwithout keeping the original file system offline.

ASM FS Snapshots can be used as a means for you to recover accidentally deleted ormodified files.

ASM FS Snapshots can be used as a source for data mining or report applications which needto work on a static, point-in-time data set.


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R2 Cluster Registry (OCR)/Voting Disk on ASM}

Automatic Storage Management (ASM) disks are used to store the OracleCluster Registry (OCR) and the voting disks. ASM Partnership and StatusTable (PST) is replicated on multiple disks and is extended to store the OCR.Consequently, the OCR tolerates loss of the same number of disks as theunderlying disk group. OCR is relocated in response to disk failures.

} ASM reserves a number of blocks at a fixed location of every ASM disk forstoring the voting disk. Should the disk holding the voting disk fail, ASMselects another disk to store this data.

} Storing the OCR and the voting disk on ASM eliminates the need to useexpensive third-party cluster volume managers or deal with the complexity ofmanaging disk partitions for OCR and voting disks in Oracle RACconfigurations.

} Create DISKGROUP contains the option for REGULAR or QUORUM Disks

} The FAILGROUP_TYPE column in both the V$ASM_DISK andV$ASM_DISK_STAT views specifies failure group type. The value for thiscolumn is REGULAR for regular failure groups and QUORUM for quorumfailure groups.


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Practices/References

} Practice view

}ASMCMD references with releases


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References:-

} Most useful information querying V$ views for ASM http://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.

2)_Documentation/server.112/e10500/asmviews.htm

Storage Administrator Guide

http://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)

_Documentation/server.112/e10500/asmviews.htm

Best book on ASM

Oracle Automatic Storage Management: Under-the-Hood & PracticalDeployment Guide by Nit in Vengu r lekar, Murali Vallath, Rich Long itinVengulerkarASM
http://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)_Documentation/server.112/e10500/asmviews.htmhttp://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)_Documentation/server.112/e10500/asmviews.htmhttp://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)_Documentation/server.112/e10500/asmviews.htmhttp://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)_Documentation/server.112/e10500/asmviews.htmhttp://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)_Documentation/server.112/e10500/asmviews.htmhttp://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)_Documentation/server.112/e10500/asmviews.htmhttp://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)_Documentation/server.112/e10500/asmviews.htmhttp://database.in2p3.fr/doc/oracle/Oracle_Database_11_Release_1_(11.2)_Documentation/server.112/e10500/asmviews.htm


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Q & A

Documents

Asm Enhancements