Hardware Requirements
*********************

Compute Node (CN)
#################

For using the *Danube Cloud* software in a production environment, we recommend using servers from IBM, Dell, HP, Cisco or Oracle server manufactures in order to achieve 100% hardware compatibility.

For list of supported hardware see `SmartOS <https://wiki.smartos.org/hardware-requirements/>`_ and `illumos <https://illumos.org/hcl/>`_ hardware compatibility lists.


Processor (CPU)
###############

*Danube Cloud* supports **Intel®** processors with the **VT-x** (Virtualization Technology eXtensions) and **EPT** (Extended Page Tables) support. Current and complete list of supported processors is available directly on the Intel® website http://ark.intel.com/Products/VirtualizationTechnology.


Memory (RAM)
############

A compute node requires a minimum of **8 GB of RAM**. The system memory can be used not only to create virtual servers, but also for operating ZFS file system. This dramatically increases the speed of read operations from hard drives (ARC).

PCI Devices (PCI)
#################

Servers using *Danube Cloud* are required to have at least **one network interface card** and a **disk controller**, which ideally allows passing disks directly to the OS (without RAID).


Network
#######

The installation procedure and run-time of *Danube Cloud* requires an **NTP server**. A **DNS server** and an **NTP server** must be accessible from the *admin* network, which is used for compute nodes and central web management intercommunication purposes.

Switch
======

*Danube Cloud* requires a 1 GbE or 10 GbE local area network (LAN). Network switches must support the IEEE 802.1Q (VLAN) standard. To achieve high availability and network aggregation, the LACP (IEEE 802.3ad) standard is used and network switches must be stackable.

.. note:: The number of virtual networks used in a data center is limited by the type of network switches used. The information about maximum number of VLANs is provided by the manufacturer of the network equipment. The usual number of supported VLANs ranges from 1024 to 4096.


Router / Firewall / VPN
=======================

A router may be required to fully leverage all network capabilities of *Danube Cloud* and effectively use networking inside :ref:`virtual data centers <datacenters>`. A router is **not required** for the installation procedure and can be deployed later as one of following options:

* **Access Zone** - software router (Solaris zone), available as an appliance at https://images.erigones.org
    * IPFILTER (IPF)

        * Router
        * Firewall

    * OpenVPN
    * Monitoring

    .. seealso:: A guide on how to create and use :ref:`access zones <access_zone>`.

* **Router / Firewall as Virtual Server** - software router (Linux/BSD/Windows).

    .. note:: For a router in a virtual server or zone, you must enable IP and MAC spoofing on a virtual network interface.

* **External hardware or software router**


Data Storage
############

Every compute node must have a local (direct-attached) storage available.
The first (main) compute node requires a local storage with at least **80 GB + <RAM size>** of disk size and other compute nodes should have at least **20 GB + <RAM size>** of local storage available.

Local or Direct-attached Storage (DAS)
======================================

Direct-attached storage is made of local data storage devices (typically hard drives) that are grouped together into disk arrays using the advanced file system and volume manager ZFS.

* SATA
* SAS
* SSD

    .. note:: Solid-state disks (SSD) can be used not only for storing data, but also 

        * as a cache for frequent synchronous disk writes of smaller data blocks (ZIL)
        * and for a rapid increase in speed of read operations of frequently used data (L2ARC).


Storage Area Network (SAN)
==========================

Using a network attached storage either through iSCSI or Fiber Channel is possible but discouraged.


.. _raid_types:

Disk Arrays (RAID)
==================

* RAID0
* RAID1
* RAID10 - provides the highest speed at random reads of small files.
* RAIDZ (RAID5) - provides maximum usability of the storage capacity as well as protection against the failure of one disk.
* RAIDZ2 (RAID6) - provides maximum usability of the storage capacity as well as protection against the failure of two disks. The performance of the array is the same as with RAIDZ.
* RAIDZ3 - provides maximum usability of the storage capacity as well as protection against the failure of three disks. The performance of the array is the same as with RAIDZ.

.. seealso:: A more detailed explanation of :ref:`disk arrays <storage>` and :ref:`disk redundancy <storage_redundancy>` can be found in a separate chapter.

* Hardware RAID

    .. warning:: When using a hardware RAID, disks must be monitored by an external monitoring system and/or by utilities provided by the OEM. The use of ZFS provides an opportunity to use all of the compute node's resources for a maximum IO performance and rigorous data protection. For disk controllers that are not able to provide direct access to hard drives (disk pass-through), use of RAID0 for every hard drive is recommended and to build a ZFS zpool on top of them.


Unsupported Hardware
********************

This section lists some of the currently unsupported hardware.

.. seealso:: Some hardware compatibility issues may be solved by adjusting the :ref:`BIOS configuration settings<bios>` of the server.