Used Software
- Clusterware: 11.2.0.3.4
- OEL 6.3
- VirtualBox 4.2.14
ACFS provides snapshotting capability for the respective filesystem. This snapshot uses the First Copy-on-Write (FCOW) methodology to enable a consistent, version-based, online view of the source filesystem.Snapshots are immutable views of the source file system as it appeared at a specific point in time.Snapshots are initially a sparse filesystem, as the source filesystem files change, the before-image extent ofthat file is copied into the snapshot directory. The before-image granularity is an ACFS extent, thus if any byte in an extent is modified, the extent is COW’ed and any subsequent changes in that extent requires no action for the snap. Note that ACFS snapshots cannot be used on filesystems that house RMAN backups,archived logs, and Datapump dumpsets.
When snapshots are created they are automatically available under the snapped filesystem as a hidden sub-directory inside the source filesystem called .ACFS. Thus no separate mount operation is needed and no separate file store needs to be maintained for the snapshots. The following example shows how to create ACFS snapshots.
Check whether we already have created any snapshots: $ /sbin/acfsutil info fs /u01/app/oracle/acfsmount/acfs_vol1 ACFS Version: 11.2.0.3.0 flags: MountPoint,Available mount time: Mon Aug 5 15:12:14 2013 volumes: 1 total size: 838860800 total free: 763121664 primary volume: /dev/asm/acfs_vol1-140 label: flags: Primary,Available,ADVM on-disk version: 39.0 allocation unit: 4096 major, minor: 251, 71681 size: 838860800 free: 763121664 ADVM diskgroup ACFS ADVM resize increment: 33554432 ADVM redundancy: mirror ADVM stripe columns: 4 ADVM stripe width: 131072 number of snapshots: 0 snapshot space usage: 0 replication status: DISABLED As we don't have created any snapshots yet - let's create one and verify the status $ /sbin/acfsutil snap create snap_001 /u01/app/oracle/acfsmount/acfs_vol1 acfsutil snap create: Snapshot operation is complete. $ /sbin/acfsutil info fs /u01/app/oracle/acfsmount/acfs_vol1 ACFS Version: 11.2.0.3.0 flags: MountPoint,Available mount time: Mon Aug 5 15:12:14 2013 volumes: 1 total size: 838860800 total free: 696012800 primary volume: /dev/asm/acfs_vol1-140 label: flags: Primary,Available,ADVM on-disk version: 39.0 allocation unit: 4096 major, minor: 251, 71681 size: 838860800 free: 696012800 ADVM diskgroup ACFS ADVM resize increment: 33554432 ADVM redundancy: mirror ADVM stripe columns: 4 ADVM stripe width: 131072 number of snapshots: 1 snapshot space usage: 49152 replication status: DISABLED Copy 2 files to our ACFS file system and create a 2.nd snapshot $ ls /u01/app/oracle/acfsmount/acfs_vol1 INFO INFO2 $ /sbin/acfsutil snap create snap_002 /u01/app/oracle/acfsmount/acfs_vol1 acfsutil snap create: Snapshot operation is complete. Checkout .ACFS directory and verify that snap_002 directory displays INFO, INFO2 files # find /u01/app/oracle/acfsmount/acfs_vol1/.ACFS /u01/app/oracle/acfsmount/acfs_vol1/.ACFS /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/.fileid /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/repl /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/repl/staging /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/repl/ready /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/repl/processed /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/repl/logs /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps/snap_001 /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps/snap_001/lost+found /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps/snap_002 /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps/snap_002/lost+found /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps/snap_002/INFO /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps/snap_002/INFO2 Remove INFO2 file from current ACFS fs $ rm /u01/app/oracle/acfsmount/acfs_vol1/INFO2 $ ls /u01/app/oracle/acfsmount/acfs_vol1 INFO Restore file from snap_002 # find /u01/app/oracle/acfsmount/acfs_vol1/.ACFS | grep INFO2 /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps/snap_002/INFO2 # cp /u01/app/oracle/acfsmount/acfs_vol1/.ACFS/snaps/snap_002/INFO2 /u01/app/oracle/acfsmount/acfs_vol1 # ls /u01/app/oracle/acfsmount/acfs_vol1 INFO INFO2
Reference:
http://www.oracle.com/technetwork/products/cloud-storage/acfs-technical-overview-514457.pdf