Pini Dibask presented on Oracle ASM concepts, architecture, and best practices. Some key points: - ASM is Oracle's recommended storage management solution and provides high performance storage for single-instance and RAC databases. - ASM uses disk groups and stripes and mirrors data across disks for redundancy and load balancing. It also rebalances data automatically during storage changes. - Administering ASM involves tasks like starting and stopping the ASM instance, managing disk groups and disks, and monitoring storage usage and I/O balance. - Best practices for ASM include using separate disk groups for data and recovery files, ensuring consistent disk performance, monitoring I/O balance, and in

1. ASM Concepts, Architecture & Best PracticesProduct Manager for Database Tools
April 24th , 2018
Pini Dibask
IOUG
Collaborate
2018

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• Pini Dibask, Product Manager for Database Tools, Quest Software
• Oracle ACE
• Oracle Certified Professional DBA (OCP)
• Public Speaker: Oracle OpenWorld, IOUG Collaborate, DOAG, OUGN, AOUG
• Blogger: OracleDBPro.BlogSpot.com
Pini.Dibask@Quest.com
http://Linkedin.com/in/pinidibask
@pini_dibask
About the Speaker

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Who is Quest Software?
9 0 % o f
F o r t u n e 1 0 0
using our
software
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engineers building
quality products
4 M
c o m m u n i t y
m e m b e r s
sharing best practices
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employees focused
on customers
Quest is a global software provider trusted by
100,000 customers and 6,000 partners in 100
countries.
We help IT organizations spend less time on
administration and more time on innovation.
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partners selling
our software

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• Toad database development &
management tools
• Foglight & Spotlight database
performance monitoring
solutions
• SharePlex for heterogeneous
database replication
Quest Database Management Solutions

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Agenda
 Concepts & Architecture
 Administration
 Best Practices
 Monitoring

6. Concepts & Architecture01

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Oracle Deployment Options – Single Instance vs. RAC
D1
D2
I1 I2 I3
D
Clustered System
(= Real Application Clusters
Nonclustered System
(= Single Instance)
Local
Storage
Shared Storage
In today’s
presentation we
will focus on this
area

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Storage Options for RAC
 ASM - Oracle’s recommended storage for Oracle Database
 DNFS (Direct Network File System)
 Unformatted partitions (aka “raw devices”) are no longer supported
 No longer supported since 12c
 Local storage is obviously not supported
 RAC requires “shared storage”

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What is ASM?
 Stands for Automatics Storage Management
 Introduced in 2003 (Oracle 10gR1)
 Volume manager and file system for Oracle database files
 Supports single-instance and Real Application Clusters (RAC)
 Oracle’s recommended storage management solution

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Why ASM?
ASM
File
System
Volume
Manager
Operating System
Application
Database
 Solves many storage management challenges
 High performance cluster file system
 Administer disk groups instead of individual disks
 Data is spread across disks to balance load
 Integrated mirroring across disks

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About Oracle ASM Instance
 Oracle ASM is built on the same technology as an Oracle Database instance
 Has SGA and background processes
 Installed in the Grid Infrastructure home
 ASM instance mounts disk groups to make ASM files available
 Does not have data files, uses control file

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About Oracle ASM Instance
 Processes
 RBAL – coordinates rebalance activity
 ARBn – One or more processes that do the rebalance activity
 DMON – Managing disk-level activities (e.g. drop)
 Memory components
 Shared Pool - metadata information
 Large Pool – parallel operations
 ASM Cache – read/write blocks during rebalance

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ASM Instance Initialization Parameters
 ASM uses a small subset of the parameters that Oracle DB instance uses

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ASM Storage Components

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ASM Disk Groups and Disks

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ASM Disk Groups and Disks

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ASM Disk Groups and Disks

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ASM for single-instance Oracle Databases

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ASM with RAC (Real Application Clusters)

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Oracle ASM Cluster with Single-Instance Oracle Database

21. Striping & Mirroring02

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RAID
 Redundant Array for Independent/Inexpensive disks
 Employs techniques of disk mirroring or disk striping (or both)
 Let’s see the most common RAID options…

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RAID 0
Source: TechTarget

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RAID 1
Source: TechTarget

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RAID 10
Source: TechTarget

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RAID 5
Source: TechTarget

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ASM Striping
 The goal of striping is to maximize storage subsystem throughput
 Balances I/O load across disks
 Reduces I/O latency by removing bottleneck from one specific disk
 Fine-grained striping - small chunks (128KB) for small I/O operations
 Coarse-grained striping – bigger chunks (equal to the AU size) for data files

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ASM Mirroring
 Protects data by storing copies of data on multiple disks
 ASM mirrors data based on file extents
 ASM supports 3 redundancy-levels
 Normal redundancy - each file extent has a single copy (2-way mirroring)
 High redundancy - each file extent has two copies (3-way mirroring)
 External redundancy - No mirroring

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Failure Groups
Disk Group “DATA”

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Mirroring Cont’d
 ASM Mirrors copies of file extents in separate failure groups
 External redundancy used in environments that use smart storage solutions
 ASM can be more flexible than traditional RAID storage mirroring
 2 Files in the same ASM Disk Group
 One file being mirrored, while the other one is not (ASM templates)

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Striping & Mirroring – External Redundancy Diagram

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Striping & Mirroring – Normal Redundancy Diagram

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Striping & Mirroring – High Redundancy Diagram

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ASM Extents
 Extents are stored in individual disks in ASM
 Consists of one or more allocation units
 Extent size = AU size for the first 20,000 extents
 Extent size = AU size * 4 for the next 20,000 extents
 Extent size = AU size * 16 for the next 20,000 extents (and higher)

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ASM Extents Cont’d

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From where does Oracle read the data?
 Example: File with 5 extents striped across eight disks in the disk group
 Reads are made against the primary extents (red blocks)

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Failure Example
 Disk H fails, therefore the extents are re-created on surviving disks

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Disk Group Rebalancing
 Automatic online rebalance during storage changes
 Only moves data proportional to storage added
 No need for manual I/O tuning
 Online migration to new storage

39. Administration03

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Accessing an ASM Instance
 SYSASM was introduced in 11gR1
 11gR1
 SYSDBA still had full administrative permissions
 Every administrative command was reported in alert log
 11gR2
 Administrative tasks can only be performed by SYSASM
 ASMSNMP should be used for read-only operations

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Example - Trying to execute administrative command in 11gR2
Not allowed via
“SYSDBA“
Allowed via
“SYSASM“

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Starting and Stopping using SQL*Plus

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Starting and Stopping using srvctl
 Server Control Utility (srvctl) can be used to start/stop ASM instances
 Server Control Utility (srvctl) can be used to check the status of ASM instances

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Starting and Stopping using ASMCMD

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Managing Disk Groups

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Adding Disks to Disk Groups

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Altering Disk Groups

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Administering via Tools - Toad for Oracle ASM Manager

49. Best Practices04

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Example of monitoring I/O activity balance
 The query below returns a value in the range of 0% - 100% to indicate the I/O balance
 DATA - Balanced
 RECO - Imbalanced
Balanced (over 80%)
Imbalanced

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Storage Preparation
 Configure at least 2 disk groups, one for Data and the other for the FRA
 Ensure all ASM disks in disk group have same performance characteristics
 Make sure all the disks in the same Oracle ASM disk group are the same size
 Minimize I/O contention ASM disks and other applications (dedicated ASM disks)
 Monitor the I/O activity balance across disks
 See: https://community.oracle.com/docs/DOC-995178
 External redundancy when using high-end storage

52. Monitoring05

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Mirroring via Dynamic Performance Views
 ASM instance hosts memory-based metadata tables (dynamic performance views)
 Below you can find the most common and useful dynamic performance views

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Monitoring via Tools

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Monitoring via Tools

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Monitoring via Tools Cont’d

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References and additional information
 Oracle Documentation
https://docs.oracle.com/database/121/OSTMG/toc.htm
 My article on Oracle Developer community - “Verifying I/O activity across disks in ASM”
https://community.oracle.com/docs/DOC-995178
 My favorite blog - Tim Hall’s Blog (ORACLE-BASE.com)
https://oracle-base.com/

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Quest provides your team with the tools to cover all of your
database platforms…
* Platform support varies from tool to tool

59. Questions?

60. Thank you