OS:
The base operating system version for FreeNAS 11.1 is FreeBSD 11.1-STABLE,
which brings in many bug fixes, performance improvements, updated and
new drivers, and new features.

OpenZFS:
There have been many improvements to OpenZFS. Users should notice a
significant speed difference when listing a large number of snapshots or
when deleting multiple snapshots and large files.

The algorithm used for scrubs and resilvers has received many speed
improvements which will be most noticeable on defragmented pools.

Resilver Priority has been added to Storage. This provides the ability to
run resilvering at a higher priority at configurable times and days of the
week.

Hardware Support:
The hardware watchdog has been reenabled for recent firmware versions of
AsrockRack C2750D4I. The BMC bug which required the watchdog to be
disabled is resolved with the 00.30.00 or newer BMC firmware version.

IPMI:
The Identify Light button has been added to make it easier to identify a
system in a rack by flashing its IPMI LED light.

Cloud:
Cloud Credentials has been added to System. This can be used to provide a
secure connection to a cloud services providers. Supported services
include Amazon S3, Azure Blob Storage, Backblaze B2, and Google Cloud
Storage.

Cloud Sync has been added to Tasks and can be used to synchronize files or
directories to remote cloud storage providers.

VMs:
VMs have received significant improvements, including:

- support for non-US keyboards.
- the ability to specify the NIC used by the VM as well as the MAC address
  for the VM NIC.
- the ability to specify the sector size used by the emulated disk.
- the ability to edit the VNC screen resolution, select the IP address to
  bind to, set the VNC password, and select the option to use the Web
  version of VNC.
- the ability to create a Docker instance based on RancherOS.

Services:
The Netdata real-time performance and monitoring system has been added.

The SNMP MIB has many improvements, including the ability to send SNMP
traps for new alerts.

Time Machine:
Support for per-backup OS X Time Machine quotas has been added.

Alerts:
The Send Test Alert button has been added to Alert Services.

The complete list of features is available at
http://doc.freenas.org/11/intro.html#new-features-in-release.