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Storage Advantages by Oracle –
Warum Redundancy Normal in ASM?
Ralf Moosandl
Senior Consultant
ralf.moosandl@trivadis.com
Nürnberg, 16.11.2010
© 2010© 20092
Trivadis facts & figures 11 Trivadis locations with more
than 540 employees
Financially independent and
sustainably profitable
Key figures 2009
Revenue CHF 100 / EUR 66 mio.
Services for more than 650 clients in over 1‘600 projects
Over 160 Service Level
Agreements
More than 5'000 training participants
Research and development
budget: CHF 5.0 / EUR 3.3 mio.
IT SOLUTIONS, SERVICES, & PRODUCTS
TECHNOLOGIES
Oracle, Microsoft, IBM, Open Source
Integration, Application Performance
Management, Security
Training Managed Services
Infrastructure
Engineering
Application
Development
Enterprise Content
Management
BUSINESS INTEGRATION SERVICES
IT
departments
Business
departments
CUSTOMER
Business
Intelligence
© 2010© 20093
Why we are special
Customer-specific
solution competence and vendor independence
offers substantiated techniques and skills as well as self-developed
approaches
guarantees repeatable quality and a safe execution
Technology competence offers more than 15 years of expertise in Oracle, Microsoft, IBM, and
open source
has its own Technology Center and strives for technological excellence
Solution and integration
expertise
has a wide and cross-sectoral customer basis and more than 1600
projects every year
Combines technological expertise with an understanding of the specific business needs of the client
Support for the entire IT
project lifecycle
has a modular portfolio of services for the entire IT project lifecycle
provides the appropriate combination of solutions and services for every „level of maturity“
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 4
Data are always
part of the game.
Nontechnical reasons for using ASM
Technical …
Reasons for using redundancies
Split Mirror
Filesystem Monitoring
Shared Pool Usage
Agenda
© 2010
Nontechnical Reasons for using ASM (1)
RAC Standard Edition is only certified with ASM
Cost savings, as customers get rid of cluster filesystems
Support of OS, Storage, DB from one vendor
Reduce costs of storage management
Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 5
© 2010
Technical reasons for using ASM (1)
Reduce administration complexity
Automatic I/O tuning for all types of workloads
Reduces the number of objects to manage, as one disk group
replaces multiple file systems
Introduces Oracle Managed Files
Simplifies database storage configuration changes
Automatic data copy on disk, add and drop
Online migration to new storage hardware
Reduced downtime
ASM prevents accidental file deletion because there is no file system
interface
Virus scanners cannot lock files within ASM ( Rtvscan.exe )
Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 6
© 2010
Technical reasons for using ASM (2)
Increase Utilization
Provides mechanism for Database Storage Consolidation
Provides clustered volume manager and file system functionality
integrated with the database
Makes block devices as simple to administer as file servers
Works with any type of disk from modular storage, NAS devices
to SAN disk arrays
Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 7
© 2010
Technical reasons for using ASM (3)
Improves Performance, Scalability, and Reliability
Raw disk I/O performance for all files
Datafiles are stored depending of filetype
Stripe files across multiple disks and storage arrays
Higher storage resource utilization
ASM-Lib API improves CPU utilization to reap I/O and provide priority
and caching hints
Overcomes file system size limitations
Implements mirroring to protect against storage array failure
Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 8
© 2010
Reasons for using redundancies (1)
Basics
File templates are collections of attribute values that are used to
specify
disk regions
file mirroring
striping attributes
for an Oracle ASM file when it is created
Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 9
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 10
File Templates – How can we handle them ?
Adding a Template to a Disk Group
Modifying a Disk Group Template
Using a User-Defined Template to Specify Attributes
Reasons for using redundancies (2)
ALTER DISKGROUP data MODIFY TEMPLATE reliable
ATTRIBUTES (COARSE);
ALTER SYSTEM SET DB_CREATE_FILE_DEST =
'+data(mytemplate)';
ALTER DISKGROUP data ADD TEMPLATE reliable
ATTRIBUTES (HIGH FINE);
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 11
Oracle ASM System Default Templates Attribute Settings
Source: Oracle® Database Storage Administrator's Guide 11g Release 2 (11.2)
Reasons for using redundancies (3)
Template Name File Striping
Mirroring,
Normal Redundancy
Mirroring,
High redundancy
CONTROLFILE FINE HIGH MIRROR
DATAFILE, ONLINELOG COARSE MIRROR MIRROR
ARCHIVELOG, BACKUPSET COARSE MIRROR MIRROR
TEMPFILE, PARAMETERFILE COARSE MIRROR MIRROR
DATAGUARDCONF, DUMPSET COARSE MIRROR MIRROR
FLASHBACK, CHANGETRACKING COARSE MIRROR MIRROR
XTRANSPORT, AUTOBACKUP COARSE MIRROR MIRROR
ASMPARAMETERFILE, OCRFILE COARSE MIRROR MIRROR
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 12
Attribute „file mirroring“ can be modified when using redundancy
normal
Permitted Values for Oracle ASM Template Redundancy Attribute
Source: Oracle® Database Storage Administrator's Guide 11g Release 2 (11.2)
Reasons for using redundancies (4)
Redundancy
Attribute Value
Resulting Mirroring
in Normal Redundancy Disk
Group
Resulting Mirroring
in High Redundancy Disk
Group
Resulting Mirroring
in External Redundancy Disk
Group
MIRROR Two-way
mirroring
Three-way
mirroring
(Not allowed)
HIGH Three-way
mirroring
Three-way
mirroring
(Not allowed)
UNPROTECTED No mirroring (Not allowed) No mirroring
© 201013
There exists another world for non database files
Reasons for using redundancies (5)
Source Oracle Corporation
Storage Advantages by Oracle - Warum Redundancy Normal im ASM?
© 201014
asmca provides a GUI interface for installing and configuring
Instances, Disk Groups, Volumes, File Systems
Reasons for using redundancies (6)
14Storage Advantages by Oracle - Warum Redundancy Normal im ASM?
© 201015
Redundancy cannot be influenced if the underlying diskgroup is
of type redundancy external
Reasons for using redundancies (7)
15Storage Advantages by Oracle - Warum Redundancy Normal im ASM?
© 201016
Redundancy can only be influenced if the underlying diskgroup is
of type redundancy normal
Reasons for using redundancies (7)
16Storage Advantages by Oracle - Warum Redundancy Normal im ASM?
© 201017
Redundancy cannot be influenced if the underlying diskgroup is
of type redundancy high
Reasons for using redundancies (7)
17Storage Advantages by Oracle - Warum Redundancy Normal im ASM?
© 2010
Reasons for using redundancies (6)
ADVM Volume characteristics can be influenced
ADVM Volume is stored in a diskgroup – if possible with
redundancy normal
Redundancy external →every kind of mirroring is
switched off
Redundancy normal →You can choose between all kinds of
mirroring for the dynamic volume
File metadata is more safe
3 mirrored extents with file metadata, visible from x$kffxp and x$kfdat
… not validated till now
Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 18
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 19
To eliminates additional layers of software complexity
Redundancy Normal or High enables customizable Redundancy
Storage system does not have a RAID controller
Mirroring across storage arrays
Extended cluster configurations
Features which need ASM mirroring
Fast Mirror Resync
Preferred Read Failure Groups
Reasons for using redundancies (7)
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 20
A failure group is a set of ASM disks that share a common failure
mechanism, such as a set of SCSI disks that share a common
SCSI Controller
Per default, every ASM disk is a failure group
Redundant copies of file extent are stored in different FGs
ASM has to take care of fulfilling redundancies
Split Mirror – Building the mirror (1)
33 2 2
SQL> SELECT name, failgroup FROM v$asm_disk;
-- without specifying
NAME FAILGROUP -- a failure group
---------------- ----------------
U01A001 U01A001
U01B001 U01B001
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 21
Minimum number of failure groups depend on redundancy
Redundancy external → 1 FG #not specified during creation
Redundancy normal → 2 FG
Redundancy high → 3 FG
ASM Mirroring at different redundancies
external normal high
Origin AU
Copy AU
Copy of copy
n AU Number
Split Mirror – Building the mirror (2)
11 11 1 1 2 33 3332 2 22 3 2
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 22
Create a logical mirror within a diskgroup
A Failure Group is a logical mirror if 2 Failure Groups exist only
Split Mirror – Building the mirror (3)
CREATE DISKGROUP U01 NORMAL REDUNDANCY
FAILGROUP U01A DISK
'/dev/sdc1' NAME U01A001,
'/dev/sdc2' NAME U01A002
FAILGROUP U01B DISK
'/dev/sdd1' NAME U01B001,
'/dev/sdd2' NAME U01B002
ATTRIBUTE
'au_size'='4M'‚ --required
'compatible.asm' = '11.2',
'compatible.RDBMS' = '11.2',
'sector_size'='512';
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 23
Shutdown the RDBMS instance
Dismount the diskgroup
Physically remove the asm disk(s) belonging to one of two failure
groups
Mount the diskgroup with force option
RDBMS Instance can be started again
Add a new failure group and rebalance
Drop the missing failure group or wait til disk_repair_time is over
Split Mirror – Activities at source site
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 24
Physically adapt the asm disk(s) of the source site
Take care of init.ora
Check ownership
Update asm_diskstring with new devicename
Mount the diskgroup with force option
Cloned Database can be used now
Add a new failure group and monitor rebalancing
Drop the missing failure group
Split Mirror – Activities at auxiliary site
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 25
All involved file templates must have redundancy mirror or high
Think about changing instance name
Think about changing DBID
Think about changing init.ora parameters
instance name
db_create_file_dest
…
Think about changing service_names
…
Split Mirror – Remarks (1)
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 26
If you run into trouble with your naming concept, binary kfed is
your friend as it can be used to edit the ASM Disk header
Header of ASM Disk stores metadata information
The disks that belong to a disk group
The amount of space that is available in a disk group
The filenames of the files in a disk group
The location of disk group data file extents
Oracle ADVM volume information
Header contains a redo log that records information about
atomically changing metadata blocks
Header can be backed up and restored by using binary kfed
Split Mirror – Remarks (2)
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 27
Problem:
You are not sure about uniqueness of file templates
maybe a DBA changed a single template to redundancy high
Solution:
Be careful and use free_mb, which does not depend on redundancies
Or use ASM command line utility, especially free_mb
Filesystem Free Space Monitoring (1)
SELECT name, free_mb
FROM v$asm_disk;
asmcmd lsdg U02
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 28
Filesystem Free Space Monitoring (2)
© 201029
Filesystem Free Space Monitoring (3)
Thresholds (1)
29Storage Advantages by Oracle - Warum Redundancy Normal im ASM?
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 30
Example Metric: Used % of Safely Usable
Description This metric shows the percentage of safely usable space used by a disk
group. Usable free space of a disk group depends on the redundancy
Data Source
Used % of Safely Usable = 100 -
(usable_file_mb/usable_total_mb)*100
where usable_total_mb = total_mb -
required_mirror_free_mb)/redundancy_factor
total_mb and required_mirror_free_mb are derived from the view
column and redundancy factor is 1 for External Redundancy Disk
Group, 2 for Normal Redundancy Disk Group, and 3 for High
Redundancy Disk Group.
Filesystem Free Space Monitoring (4)
© 201031
Filesystem Free Space Monitoring (5)
Thresholds (2)
31Storage Advantages by Oracle - Warum Redundancy Normal im ASM?
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 32
Apply the following rules to the sum of space used by datafiles,
tempfiles and redo-logs:
For disk groups using external redundancy,every 100 GB of space need 1 MB of extra shared pool plus 2 MB
For disk groups using normal redundancy,
every 50 GB of space need 1 MB of extra shared pool plus 4 MB
For disk groups using high redundancy,
every 33 GB of space need 1 MB of extra shared pool plus 6 MB
Consider also the sum of space used by archived redo logs
if you are dealing with a huge Flash Recovery Area
ACFS Volumes also need resources
Shared Pool Usage - ASM Instance
SHARED_POOL_SIZE = '128M'
TBP
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 33
Query V$SGASTAT
to see how much memory is allocated for extent pointers in an
RDBMS instance. Doc ID 465039.1
Shared Pool Usage - RDBMS Instance (1)
SELECT * FROM V$SGASTAT
WHERE name= 'ASM extent pointer array';
© 2010Storage Advantages by Oracle - Warum Redundancy Normal im ASM? 34
Shared Pool Usage - RDBMS Instance (2)
© 201035
ASM Redundancies – Core Messages
Knowledge
transfer is only
the beginning.
Knowledge
application is
what counts.
You should use ASM
Yes, you can
There are good reasons for
redundacy normal
Split Mirror works
Rely on absolute (free space)/3 only
and read metric definitions carefully
Shared Pool Need is negligible
O-Storage - ASM ConceptsStorage Advantages by Oracle - Warum Redundancy Normal im ASM?