Benefits of Oracle ACFS
Benefits Oracle ACFS
An Oracle White Paper
January 2015
Benefits of Oracle ACFS
Benefits Oracle ACFS
Introduction ....................................................................................... 1
Performance ...................................................................................... 2
Oracle ACFS Advanced Functionality ................................................ 4
Simple Point-in-Time Read-Write Snapshots ................................. 4
Oracle ACFS High Availability NFS Services ................................. 4
Oracle ACFS Tagging ................................................................... 5
Oracle ACFS Replication ............................................................... 5
Oracle ACFS Security ................................................................... 5
Oracle ACFS Encryption................................................................ 6
Oracle ACFS Auditing ................................................................... 6
Self-Tuning and Resilience ................................................................ 6
Disk Space Scalability and Performance Factors........................... 7
Automatic Resource Management and Automation ....................... 7
Oracle ACFS on Oracle Database Appliance .................................... 8
Oracle ACFS on Linux Exadata Database Machines ......................... 9
Oracle ACFS Use Cases ................................................................. 10
Conclusion ...................................................................................... 11
Benefits Oracle ACFS
Oracle ASM Cluster File System (ACFS) provides unprecedented simplicity, automation
and functionality in storage and file management for all file types including Oracle
database and general purpose files.
Oracle ACFS is a general-purpose industry standard POSIX, X/OPEN and Windows
compliant cluster file system supporting multiple operating systems and server
platforms, including Oracle Exadata Database Machine, Oracle Database Appliance
(ODA) and traditional server environments. Oracle ACFS includes advanced features
such as file system snapshot, replication, tagging, security, encryption, auditing and
highly available NFS (HANFS) services.
Oracle ACFS/ASM software stack is bundled with a general purpose cluster volume
manager, the Oracle ASM Dynamic Volume Manager (Oracle ADVM), which provides
common volume management services and a standard device driver interface for
system administrators to manage volumes across different nodes of a cluster with the
same functionality on multiple platforms.
Oracle Database and Oracle ACFS both are clients of Oracle Automatic Storage
Management (ASM). Oracle ACFS makes use of ASM files and inherits ASM file features
including striping, mirroring, rebalancing, intelligent data placement, preferred read,
fast resync, even read, flex ASM and other features.
The combination of Oracle ACFS, ADVM, Oracle ASM and Oracle Clusterware make up
the Oracle Grid Infrastructure (GI). Oracle GI is a tightly integrated foundation to
manage databases, volumes and file systems in cluster environments. Oracle GI
simplifies storage and cluster management, and greatly reduces complexity and costs by
eliminating the need for 3rd party software.
Oracle ACFS management is streamlined through one management interface, one set of
installation and configuration tools, one cluster framework and one vendor for support.
The product provides a scalable solution designed to reduce the total cost of ownership,
to simplify system and storage management, and to provide high performance without
the need for custom tuning. Oracle ACFS optimizes utilization through consolidation
and ensures file system availability.
Benefits Oracle ACFS
Oracle ACFS is designed to deliver the best possible performance with Oracle databases
and general purpose files. Oracle ACFS obtains an extent map list and disk list
information from the Oracle ASM instance whenever it opens an ASM file. This means,
neither Oracle ASM nor Oracle ACFS are in the I/O path when accessing files on disk.
Oracle ACFS caches ASM disk mapping information and uses that information on
subsequent ACFS I/O operations to directly read and write to ASM disk group disks.
Oracle ACFS provides a direct I/O path from the database through to the ASM disk group
devices and bypasses the traditional OS VM page caching mechanism used for file
system applications. This model enables databases configured to use ACFS to achieve
performance metrics comparable to databases configured to use Oracle ASM directly.
Comprehensive internal benchmarks using OLTP and DSS workloads have proven the
performance of Oracle ACFS and ASM to be similar. The following is a summary of the
performance data and the benchmark environment used for those tests:
Hardware: Two node Linux cluster with 72 GB RAM and 12 CPUs
Software: Swingbench, Oracle Database 12c
Storage: Two ASM disk groups with normal redundancy setup
• one disk group for data and one for the recovery area
• For data, 5 shelves of the disk array were used, total of 80 physical disks, configured
as RAID10. In case of DSS 120 disks on 5 shelves were used.
• For recovery area, 1 shelf was used, total of 16 physical disks, configured as RAID 10.
• The disk groups were created with enough space to accommodate 2 databases: one
of them using ACFS and the other using ASM directly.
• One ACFS file system was created on each of the above disk groups.
• Two identical databases were configured, with files stored in ACFS and ASM.
• Two database instances per database were used.
• Archivelog and flashback database enabled (disabled for DSS).
Swingbench Schema:
• OE Schema (OLTP) created with version 2, no partitioning, no compression,
bigfile tablespace, all indexes, sizing factor 6 (= 19 GB Tablespace)
• SH Schema (DSS) created with range partitioning, no compression, bigfile
tablespace, all indexes, sizing factor 41 (= 70 GB Tablespace)
Benefits Oracle ACFS
The following chart shows performance based on OLTP workload. As you can see, the
throughput performance and transaction response time are almost identical regardless
of whether the database use ACFS or ASM directly.
OE workload throughput
Transactions per second
Response time (ms)
BT transaction performance
Number of users
Number of users
The operating system and CPU loads show no significant difference between Oracle
ACFS and ASM; neither did the DSS workload as shown in the following:
IO Performance - Throughput
CPU utilization
Throughput (MB/s)
CPU utilization (%)
Number of users
Number of users
% diff
SH throughput (TX/min)
IO throughput (Reads / sec)
IO throughput (MB Read / sec)
CPU usage (%)
DSS workload response time:
Benefits Oracle ACFS
Response time (sec)
% diff
Oracle ACFS Advanced Functionality
Simple Point-in-Time Read-Write Snapshots
An Oracle ACFS snapshot is an online, read-only or read-write, point in time copy of an
Oracle ACFS file system. The snapshot copy is space-efficient and uses Copy-On-Write
functionality. Before an Oracle ACFS file extent is modified or deleted, its current value
is preserved in the snapshot to maintain the point-in-time view of the file system.
Oracle ACFS supports 1023 RO/RW snapshots and snaps of snapshots allowing a
complete hierarchy of snapshots for any file system, with the ability to arbitrarily delete
or add a snapshot anywhere in the hierarchy and support full inheritance.
Oracle ACFS snapshot storage is maintained within the file system, eliminating the
management of separate storage pools for file systems and snapshots. All ACFS
snapshots are always available when the ACFS file system is mounted. Oracle ACFS file
systems can be dynamically resized online to accommodate additional file and snapshot
storage requirements.
Oracle ACFS High Availability NFS Services
High Availability Network File Storage (HANFS) for Oracle Grid
Infrastructure provides un-interrupted service of NFS v2/v3/v4
exported paths by exposing NFS exports on Highly Available Virtual
IPs (HAVIP). Oracle Clusterware agents ensure that the HAVIPs and
NFS exports are always online. If a cluster node fails, the HAVIP and
NFS services are automatically taken over by a surviving node.
The HANFS feature enables highly available NFS servers to be
configured using Oracle ACFS clusters. The HANFS cluster
configurations may be built from your existing infrastructure or commodity servers and
storage. This provides network services similar to ‘network filer’ at the fraction of the
Benefits Oracle ACFS
Oracle ACFS Tagging
Oracle ACFS Tagging is a feature that allows a user to associate one or more files
together as a group by assigning a unique ‘tag name’ attribute. Group operations can be
performed based on tagged files that may span across different directories within an
Oracle ACFS file system and within a single node or a cluster. Different groups of tagged
files (e.g. ‘medical imaging’, ‘photo album’, etc) may be replicated as groups of related
files, complementing the replication of database files using Oracle Data Guard.
Oracle ACFS Replication
Oracle ACFS Replication is a Disaster Recovery (DR) solution that enables replication of
an Oracle ACFS file system across the network from a primary to a standby site,
providing disaster recovery capability for the file system. Either the primary or the
standby sites can be a single node or a cluster of nodes. A primary site for one file
system can be the standby site for a different file system and vice-versa.
Oracle ACFS Replication captures file updates in real-time and transfers changes
asynchronously to the standby file system. The standby file system is available for
reading and RW snapshot of the RO file system can be created. The standby file system
is available in read-only mode during replication, however, read-write snapshots of the
file system can be created for other applications.
Oracle ACFS Replication complements Oracle Data Guard and provides the customer
with an end-to-end DR solution for all files. The transaction time stamps are recorded
within the log files so that recovery can be synchronized with Oracle Data Guard for fail
over or role reversal.
Oracle ACFS Security
Oracle ACFS Security can be used to protect sensitive data from internal and external
threats by providing fine-grained access control on top of the access control offered by
the operating system.
Oracle ACFS Security provides realm-based security for Oracle ACFS file systems
enabling users to create realms and specify security policies for users and groups and
thereby control access on file system objects. Oracle ACFS Security uses realms, rules,
rule sets, and command rules to enforce security policies. The Oracle ACFS realm is a
virtual container of files and directories for which access is defined by security filters.
Benefits Oracle ACFS
Oracle ACFS Encryption
Encryption is a feature that helps meeting regulatory compliance requirements by
keeping data in an Oracle ACFS file system in an encrypted format. . Oracle ACFS
Encryption enables users to encrypt data stored on disk (data-at-rest) and provides
secured encryption keys to decode data, thereby protecting against unauthorized use of
such data in the case of data loss or theft.
Oracle ACFS Encryption can be applied to the entire file system or just individual files
and directories. It is completely transparent to authorized users. In addition,
applications work unchanged with encrypted files. Encrypted and unencrypted files can
co-exist on the same file system. System administrators and Oracle ACFS security
administrators can initiate encryption operations.
Using Oracle ACFS Encryption, each file is protected by two keys, the File Encryption Key
(FEK) and the Volume Encryption Key (VEK). File data is encrypted using a unique FEK;
the FEK is stored on disk, and is encrypted using a VEK. VEKs are stored in an Oracle
Wallet and can be password protected.
Oracle ACFS Auditing
Oracle ACFS Auditing provides auditing capabilities for Oracle ACFS security and
encryption. This auditing framework produces a separate audit trail, or audit source, for
each Oracle ACFS file system on each individual node, and enforces separation of duties
regarding the management and review of the audit source.
Audit sources, can be generated from Oracle Database audit trail tables, database
operating system audit files, and database redo logs. Both Oracle ACFS security and
encryption are also audit sources, and these sources can be enabled and disabled by an
Oracle ACFS audit manager.
Self-Tuning and Resilience
Oracle ACFS supports large files with 64-bit file and file system data structure sizes
leading to exabyte capable file and file system capacities on 64 bit platforms. Variable
extent-based storage allocation and high-performance directories contribute to fast
performance and shared disk configurations that provide direct storage paths to Oracle
ACFS data from each cluster member. File system integrity and fast recovery is achieved
with Oracle ACFS metadata checksums and journaling.
Benefits Oracle ACFS
Oracle ACFS is designed as a multi-node, shared file system model that delivers
coherent, cached, direct storage paths to Oracle ACFS file system data. It presents single
system file access semantics across cluster configurations. Applications and users on all
cluster members are always presented with the same view of shared Oracle ACFS file
data, supported by cluster-wide user and metadata cache coherency mechanism.
Disk Space Scalability and Performance Factors
Oracle ACFS supports 2^40 (1 trillion) files in a file system. Oracle ACFS supports 256
mounted file systems on 64-bit systems. However, more file systems can be mounted if
there is adequate memory. ACFS makes use of 4K block size allocation units and up to
128MB extent sizes when managing ACFS file storage. Benchmarks have shown that the
4k default block size works best in all cases and therefore eliminates the need for
tuning. ACFS automatically issues storage disk I/Os in sizes up to the maximum
supported by the storage I/O subsystem eliminating the need for per-OS consideration
and configuration.
Oracle ACFS pre-allocates large user files to improve performance when writing data.
Oracle ACFS also allocates local metadata files when nodes mount the file system for the
first time. Oracle ACFS keeps local bitmaps available to reduce contention on the global
storage bitmap when searching for free space. This disk space is reported as “in-use” by
tools such as the UNIX df command, although some of the space may not actually be
allocated as of yet. This local storage pool can be as large as 128 megabytes per node
and can allow space allocations to succeed, while commands such as df report less
space available than what is being allocated.
Automatic Resource Management and Automation
Oracle Clusterware resources support Oracle ACFS, Oracle ADVM, and Oracle Kernel
Services Driver (OKS) startup, cluster mount registry, and single file system startup,
shutdown, and steady-state actions. These resources are configured automatically at
installation time and therefore do not require any management. The drivers are
managed as a single resource set.
Whenever Oracle Clusterware is started on a cluster node, the Oracle ACFS startup
operations for the node consult the cluster mount registry and attempt to mount all
Oracle ACFS file systems that are registered for this node.
In order to manage dependent resources as a single item, an Oracle ACFS file system
configured as the underlying file system for an Oracle Database home, includes a
Benefits Oracle ACFS
resource dependency to the Oracle Database. This dependency causes the stack to be
started and the file system to be automatically mounted prior to the Oracle Database
being started.
Oracle ACFS on Oracle Database Appliance
The 12.1.2 Oracle Database Appliance (ODA) release(s) has adopted Oracle ASM Cluster
File System (ACFS) as the primary cluster file system to store database files and general
purpose data. Three default file system are created automatically in the Oracle
Database Appliance ASM disk groups (DATA, RECO, and REDO) when using the 12.1.2
release. When new databases are created, the associated database files are created in
these three ACFS file systems instead of in the ASM disk groups directly.
Note that when you are upgrading from a previous release to 12.1.2, the databases that
were previously created on ASM are not automatically moved to ACFS, but can co-exist
with the new databases that are created on ACFS. Customers can choose to migrate
existing databases from ASM to ACFS post-upgrade by following the steps outlined in
the white paper titled ‘Steps to Migrate Non-CDB databases to ACFS on ODA 12.1.2’.
Oracle ACFS was chosen as the primary file system for Oracle Database Appliance
because it provides:
Increased functionality without requiring additional management
Equivalent performance to Oracle ASM
Industry standard and simple user interface
Database snapshots to quickly and easily provision test and development
environments at a fraction of the disk storage required with full database copies
Advanced functionality for general purpose files such as replication, tagging,
encryption, security, and auditing
Oracle ACFS file systems benefit from all the Oracle ASM functionality such as striping,
mirroring, rebalancing and dynamic capacity management that make both Oracle ASM
and ACFS highly performing, scalable and highly available platforms.
Database creation on ACFS follows the same Oracle Managed Files (OMF) principles that
are used with Oracle ASM. For every database creation, new directories are created in
Benefits Oracle ACFS
DATA, RECO, and REDO file systems for the new database files (similar to Oracle ASM).
Oracle ACFS in the Oracle Database Appliance requires no administration. The
Appliance Manager automatically manages the storage; including ACFS file systems and
the underlying ASM disk groups.
Internal testing of database workloads has show similar performance for Oracle ACFS
and ASM. Both Oracle ACFS and ASM provide direct I/O to disk resulting in high
performance for database files. In addition, Oracle ACFS performs buffered I/O for nondatabase files that benefit from cached data in the system memory. The workload
performance details are described in the ‘performance’ section of this paper.
Oracle ACFS on Linux Exadata Database Machines
Starting with Oracle Grid Infrastructure 12c Release, Oracle ACFS supports all
database files and general purpose files on Oracle Exadata Database Machine running
Oracle Linux on database servers. This makes ACFS an attractive storage alternative for
data loads, extracts, migrations, and other use cases for storing general purpose files.
In addition, Oracle ACFS supports database files on Oracle Exadata Database Machines,
specifically; Oracle ACFS supports all database file types for the following database
Oracle Database 10g Rel. 2 ( and
Oracle Database 11g ( and higher)
Oracle Database 12c ( and higher)
Please note that Oracle ACFS does not currently support the Oracle Smart Scan
(predicate processing) and is not able to push database operations directly to storage.
For best performance, store database files on the Exadata Storage using ASM. Since
Exadata Storage Servers do not support Oracle Database 10g, Oracle ACFS provides a
storage option for customers wishing to host older databases on their Exadata server.
Also, while Oracle ACFS snapshots and tagging are supported for database files, Oracle
ACFS replication and security/encryption/audit are only supported with general purpose
files, and cannot be used with database files.
Oracle ACFS supports all database file types and general purpose files. All Oracle ACFS
advanced functionality on the Exadata platform are supported for general purpose files
including snapshots, replication, tagging, security, encryption, audit and HANFS.
Benefits Oracle ACFS
Oracle ACFS Use Cases
Oracle ACFS is a true cache coherent cluster file system supporting concurrent readwrite operations guaranteeing that clients on all nodes of the cluster have exactly the
same consistent view of data. There is no extra effort to install ACFS since it is installed
during the Oracle Grid Infrastructure deployment and is easily configurable for different
use cases in your environment.
Oracle ACFS is the ideal file system for Oracle RAC cluster and standalone deployments
as well as Oracle application and middleware environments, while it can be used with
other any application vendor. The typical use cases for ACFS are:
Support 10g Oracle Databases on Linux based Oracle Exadata Database Machines.
This makes Exadata a more flexible platform enabling consolidation and easy
migration for customers.
o Benefit: Consolidation
Store Business data and unstructured data such as scanned documents, image files,
and BLOB data types in an Oracle ACFS file system as an alternative to storing them
inside a database.
Use Oracle ACFS for shared Oracle Database Homes and as a data store for all
administrative, log files, trace and audit files.
Benefit: No need to use 3rd party solutions
Consolidate monitoring of audit files and log files from many systems in your data
center using Oracle ACFS Replication (audit and log files can be configured to be
replicated into one Monitoring server.
Benefit: Manage and share one set of binaries and administrative files
Facilitate Oracle ACFS Replication to complement Oracle Data Guard (DR for Oracle
Databases) as a DR solution for all non-database files. This allows for Database
recovery to be synchronized with the Oracle ACFS file system by leveraging the new
‘time stamp’ feature introduced in Oracle ACFS
Benefits: Ease of use and manipulations
Benefits: Centralize your monitoring and simplify management
Use Oracle ACFS snapshots for creating point in time snapshots. The read-write
snapshots allow you to present data for test and development environment and
Benefits Oracle ACFS
also allow for taking backups on demand. The ‘gDBClone’ script that is downloadable from the Oracle Technology Network together with a best practice white paper
facilitates ACFS snapshots for an easy deployment and management of test and
development environments.
Use Oracle ACFS NFS/CIFS network protocols to deliver NFS/CIFS exported file
systems and leverage the HANFS feature to provide highly available network file
systems to clients.
Benefits: Highly available and simple sharing of file systems across the
Oracle ACFS Security and Encryption features are complimentary solution to Oracle
Advanced Security Option (ASO) and Data Vault for the general purpose files. This
feature may be used for a highly granular file access control and encryption for data
at rest.
Benefits: Eliminate 3rd party snapshot solutions and automate database
Benefits: Tighter file access control and data file protection through
Oracle ACFS Tagging feature enables group operations through ‘tags’. A great
application of Tagging is to use it in conjunction with ACFS Replication and allow
only the tagged files to be replicated.
Benefits: Ease of management
Oracle customers benefit from a single integrated solution designed to manage general
purpose data as well as database data across multiple operating system platforms
including Oracle Exadata Database Machine, Oracle Database Appliance and traditional
non-engineered servers with one management interface, one set of installation and
configuration tools, one clusterware framework and a single vendor for support. Oracle
ASM and ACFS eliminate the need for 3rd party volume managers and file systems on
Oracle platforms greatly simplifying the storage management stack.
Oracle ACFS and Oracle ASM are designed to be always-on-line, increasing file system
and database availability despite storage hardware failures and storage configuration
Benefits Oracle ACFS
changes. Oracle ACFS continues to bring innovations in automation to further simplify
file and storage management. Oracle ACFS, when combined with Oracle ASM, provide
for the highest performance and continuous balanced I/O distribution without tedious
complex administration. They provide a scalable solution that makes them suitable for
very small as well as multi-hundred terabyte file systems. Oracle ASM disk groups
function as storage containers that are ideal for consolidation of databases and file
systems that result in optimal storage utilization and reduce the storage waste in
computing environments.
Benefits Oracle ACFS
January 2015 Update
Author: Ara Shakian
Oracle Corporation
World Headquarters
500 Oracle Parkway
Redwood Shores, CA 94065
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