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Storage Foundation 7.4.1 Administrator's Guide - Linux

Last Published: 2019-09-25

Product(s): InfoScale & Storage Foundation (7.4.1)

Platform: Linux

Deduplicating data

You deduplicate data using the fsdedupadm command. The fsdedupadm command performs the following functions:

Functionality	Command syntax
Enable the deduplication of a file system.	`fsdedupadm enable [-c chunk_size] [-q] mount_point`
Disable the deduplication of a file system.	`fsdedupadm disable [-q] mount_point`
Query the deduplication configuration of a file system.	`fsdedupadm list mount_point\|all`
Start a deduplication run on a file system.	`fsdedupadm start [-s] [-q] mount_point`
Stop a deduplication run on a file system.	`fsdedupadm stop [-q] mount_point`
Query the deduplication status of a file system.	`fsdedupadm status mount_point\|all`
Enable or disable the skipping of shared extents.	`fsdedupadm skipshared {true\|false} mount_point`
Set the node on which the scheduled deduplication job will run.	`fsdedupadm setnodelist nodelist mount_point\|all`
Set the deduplication schedule for a file system.	`fsdedupadm setschedule time mount_point`
Initiate a deduplication dry run on a file system.	`fsdedupadm dryrun [-o threshold=#] mount_point`
Remove the deduplication configuration file and deduplication database on a file system.	`fsdedupadm remove mount_point`

For more information about the keywords, see the fsdedupadm(1M) manual page.

The following example creates a file system, creates duplicate data on the file system, and deduplicates the file system.

Example of deduplicating a file system

Create the file system fsvol1:
```
# mkfs -t vxfs /dev/vx/rdsk/fsdg/fsvol1
```

Mount the file system as /mnt1:

# mount -t vxfs /dev/vx/dsk/fsdg/fsvol1 /mnt1

Make a temporary directory, temp1, on /mnt1 and copy the file1 file into the directory:

# mkdir /mnt1/temp1
# cd /mnt1/temp1
# cp /root/file1 .
# /opt/VRTS/bin/fsadm -S shared /mnt1

Mountpoint    Size(KB)    Available(KB)   Used(KB)   Logical_Size(KB) Space_Saved(KB)
          /mnt1        20971520      19335962      346609           602609        0

The file1 file is approximately 250 MB, as shown by the output of the fsadm command.

Make another temporary directory, temp2, and copy the same file, file1, into the new directory:
```
# mkdir /mnt1/temp2
# cd /mnt1/temp2
# cp /root/file1 .
# /opt/VRTS/bin/fsadm -S shared /mnt1
```
```
Mountpoint  Size(KB) Available(KB) Used(KB) Logical_Size(KB) Space_Saved(KB)
/mnt1       4194304  3588700       548740   548740           0%
```
By copying the same file into temp2, you now have duplicate data. The output of the fsadm command show that you are now using twice the amount of space.

Enable deduplication on the mount point /mnt1:

# /opt/VRTS/bin/fsdedupadm enable -c 4096 /mnt1
# /opt/VRTS/bin/fsdedupadm list /mnt1

 
Chunksize Enabled SkipShared Schedule NodeList            Filesystem
---------------------------------------------------------------------
4096      YES     True       NONE     node1               /mnt1

Start a deduplication run on the mount point /mnt1:

# /opt/VRTS/bin/fsdedupadm start /mnt1
UX:vxfs fsdedupadm: INFO: V-3-20: 0000: deduplication is started
on /mnt1.

Check status of deduplication:

# /opt/VRTS/bin/fsdedupadm status /mnt1
Saving    Status    Node            Type        Filesystem
--------------------------------------------------------------------------------
42%       COMPLETED fsaixp702-v05   MANUAL      /mnt1
2014/09/23 22:48:22 Begin full scan.
2014/09/23 22:51:45 End detecting duplicates and filesystem changes.

Verify that the file system was deduplicated by checking how much space you are using:

# /opt/VRTS/bin/fsadm -S shared /mnt1

Mountpoint    Size(KB)    Available(KB)   Used(KB)   Logical_Size(KB) Space_Saved(KB)
             /mnt1       20971520      19335962       346609           602609        256000

The output shows that the used space is nearly identical to when you had only one copy of the file1 file on the file system.