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WAN Optimization

Toggle Disk Usage for logging or wan-opt (290892)

Both logging and WAN Optimization use hard disk space to save data. For FortiOS 5.4 you cannot use the same hard disk for WAN Optimization and logging.

  • If the FortiGate has one hard disk, then it can be used for either disk logging or WAN optimization, but not both. By default, the hard disk is used for disk logging.
  • If the FortiGate has two hard disks, then one disk is always used for disk logging and the other disk is always used for WAN optimization.
note icon WAN Optimization is not supported while the FortiGate is in Flow-based inspection.

On  the FortiGate, go to System > Advanced > Disk Settings to switch between Local Log and WAN Optimization.

You can also change disk usage from the CLI using the following command:

configure system global

set disk-usage {log | wanopt}


note icon The Toggle Disk Usage feature is supported on all new "E" Series models, while support for "D" Series models may vary.

Please refer to the Feature Platform Matrix for more information.


caution icon Changing the disk setting formats the disk, erases current data stored on the disk and disables either disk logging or WAN Optimization.

You can configure WAN Optimization from the CLI or the GUI. To configure WAN Optimization from the GUI you must go to System > Feature Select and turn on WAN Optimization.

note icon Remote logging (including logging to FortiAnalyzer and remote Syslog servers) is not affected by using the single local hard disk for WAN Optimization.

Enabling WAN Optimization affects more than just disk logging

In addition to affecting WAN Optimization, the following table shows other features affected by the FortiGate disk configuration.

Features affected by Disk Usage as per the number of internal hard disks on the FortiGate
Feature Logging Only
(1 hard disk)
WAN Opt. Only
(1 hard disk)
Logging & WAN Opt.
(2 hard disks)
Logging Supported
Not supported Supported
Report/Historical FortiView Supported Not supported Supported
Firewall Packet Capture (Policy Capture and Interface Capture) Supported Not supported Supported
AV Quarantine Supported Not supported Supported
IPS Packet Capture Supported. Not supported Supported
DLP Archive Supported Not supported Supported
Sandbox DB & Results FortiSandbox database and results are also stored on disk, but will not be affected by this feature.

MAPI AV scanning is supported over WAN Optimization (267975)

AV works on MAPI when WAN Optimization is used.