G291-Z20 ‏(rev. A00)‏

(rev.100)

HPC Server - 2U 8 x GPU Server | Application: AI , AI Training , AI Inference & HPC

Application:

AI AI Training AI Inference HPC

Supports up to 8 x double slot GPU cards
AMD EPYC™ 7002 and 7001 series processor family
8-Channel RDIMM/LRDIMM DDR4, 8 x DIMMs
2 x SFP+ 10Gb/s LAN ports (Mellanox^® ConnectX-4 Lx)
1 x Dedicated management port
8 x 2.5" hot-swappable HDD/SSD bays
2 x M.2 with PCIe Gen3 x4/x2 interface
8 x PCIe Gen3 expansion slots for GPUs
2 x PCIe x16 half-length low-profile slots for add-on cards
Aspeed^® AST2500 remote management controller
Dual 2200W 80 PLUS Platinum redundant/hot-swap power supply
Optimized performance with Mellanox Infiniband EDR and Ethernet 100G products

Request a Quote

مقارنة

1/4

Select All

Cancel All Download

* كل المعلومات المذكورة للاطلاع فقط. وتحتفظ جيجابايت بالحق في تعديلها أو مراجعتها في أي وقت دون اخطار مسبق.
* مستوى الأداء المعروض اعتماداً على أقصي القيم الافتراضية للواجهات والتي زودنا بها المصنعين المختلفين والذين وضعوا المعايير القياسية لهذه الواجهات. وقد يختلف مستوى الأداء الفعلي باختلاف مواصفات الحاسب.
* كل العلامات التجارية والشعارات هي ملك لحامليها.
* نظرأً لخصائص الحاسب القياسية، فإن قدراً من السعة الكلية للذاكرة يتم استخدامه من قبل الحاسب ولذلك تصبح سعة الذاكرة الحقيقية أقل من السعة المذكورة على وحدات الذاكرة.

SPECIFICATIONS

Dimensions (WxHxD, mm)

2U
448 x 87.5 x 800

Motherboard

MZ21-G20

CPU

AMD EPYC™ 7002 series processor family
Single processor, 7nm, Socket SP3
Up to 64-core, 128 threads per processor
TDP up to 225W, cTDP up to 240W

Fully support 280W

Compatible with AMD EPYC™ 7001 series processor family

Socket

Socket SP3

Chipset

System on Chip

Memory

8 x DIMM slots
DDR4 memory supported only
8-Channel memory architecture
RDIMM modules up to 128GB supported
LRDIMM modules up to 128GB supported
Memory speed: Up to 3200*/ 2933 MHz

- Note:
* Follow BIOS setting and memory QVL list if running 3200 Mhz

LAN

2 x SFP+ 10Gb/s LAN ports (Mellanox^® ConnectX-4 Lx)
1 x 10/100/1000 management LAN

Video

Integrated in Aspeed^® AST2500
2D Video Graphic Adapter with PCIe bus interface
1920x1200@60Hz 32bpp, DDR4 SDRAM

Audio

N/A

Storage

8 x 2.5" hot-swappable HDD/SSD bays
SAS card is required for SAS devices support

Recommended 12Gb/s SAS cards:
CRA4448
CRA4548

SAS

N/A

RAID

N/A

Peripheral Drives

N/A

Expansion Slots

8 x PCIe x16 slots (Gen3 x16 bus) for GPUs
2 x PCIe x16 (Gen3 x16 bus) Half-length low-profile slots

1 x M.2 slot:
- M-key
- PCIe Gen3 x4
- Supports NGFF-2242/2260/2280/22110 cards

1 x M.2 slot:
- M-key
- PCIe Gen3 x2
- Supports NGFF-2242/2260/2280/22110 cards

- Maximum limitation of GPU card: 285mm (L) x 111.5mm (W) x 39.5mm (H)
- System is validated for population with a uniform GPU model
- Support is not provided for mixed GPU populations
- For the latest GPU cards QVL, please contact your GIGABYTE representative

Internal I/O

1 x TPM header
1 x Sli-SAS connectors
2 x M.2 slots
1 x Serial header
1 x Buzzer

Front I/O

1 x Power button with LED
1 x ID button with LED
2 x LAN activity LEDs
1 x HDD activity LED
1 x System status LED
1 x Reset button

Rear I/O

2 x USB 3.0
1 x VGA
2 x SFP+
1 x MLAN
1 x Power button with LED
1 x ID button with LED
1 x Reset button
1 x NMI button
1 x System status LED

Backplane I/O

8 x SAS/SATA ports
Bandwidth: SATAIII 6Gb/s or SAS 12Gb/s per port
SAS card is required for SAS devices support

TPM

1 x TPM header with LPC interface
Optional TPM2.0 kit: CTM000

Power Supply

2 x 2200W redundant PSUs
80 PLUS Platinum

AC Input:
- 100-127V~/ 14A, 47-63Hz
- 200-240V~/ 12.6A, 47-63Hz

DC Output:
- Max 1200W/ 100-127V~
+12.12V/ 95.6A
+12Vsb/ 3.5A
- Max 2200W/ 200-240V
+12.12V/ 178.1A
+12Vsb/ 3.5A

NOTE: The system power supply requires C19 type power cord

System Management

Aspeed^® AST2500 management controller
GIGABYTE Management Console (AMI MegaRAC SP-X) web interface

Dashboard
JAVA Based Serial Over LAN
HTML5 KVM
Sensor Monitor (Voltage, RPM, Temperature, CPU Status …etc.)
Sensor Reading History Data
FRU Information
SEL Log in Linear Storage / Circular Storage Policy
Hardware Inventory
Fan Profile
System Firewall
Power Consumption
Power Control
LDAP / AD / RADIUS Support
Backup & Restore Configuration
Remote BIOS/BMC/CPLD Update
Event Log Filter
User Management
Media Redirection Settings
PAM Order Settings
SSL Settings
SMTP Settings

OS Compatibility

For AMD EPYC™ 7002 series processor family

Windows Server 2016 ( X2APIC/256T not supported)
Windows Server 2019

Red Hat Enterprise Linux 7.6 ( x64) or later
Red Hat Enterprise Linux 8.0 ( x64) or later

SUSE Linux Enterprise Server 12 SP4 ( x64) or later
SUSE Linux Enterprise Server 15 SP1 ( x64) or later

Ubuntu 16.04.6 LTS (x64) or later
Ubuntu 18.04.3 LTS (x64) or later
Ubuntu 20.04 LTS (x64) or later

VMware ESXi 6.5 EP15 or later
VMware ESXi 6.7 Update3 or later
VMware ESXi 7.0 or later

Citrix Hypervisor 8.1.0 or later

For AMD EPYC™ 7001 series processor family

Windows Server 2012 R2 with Update
Windows Server 2016

Red Hat Enterprise Linux 7.4 (x64) or later
Red Hat Enterprise Linux 8.0 ( x64) or later

SUSE Linux Enterprise Server 11.4 (x64) or later
SUSE Linux Enterprise Server 12.3 (x64) or later
SUSE Linux Enterprise Server 15 (x64) or later

Ubuntu 16.04 LTS (x64) or later
Ubuntu 18.04 LTS (x64) or later
Ubuntu 20.04 LTS (x64) or later

VMware ESXi 6.5 Update1 or later
VMware ESXi 6.7 or later
VMware ESXi 7.0 or later

Citrix Xenserver 7.1.0 CU2 or later
Citrix Xenserver 7.4.0 or later
Citrix Hypervisor 8.0.0 or later

System Fans

8 x 80x80x38mm (15000rpm)

Operating Properties

Operating temperature: 10°C to 35°C
Operating humidity: 8%-80% (non-condensing)
Non-operating temperature: -40°C to 60°C
Non-operating humidity: 20%-95% (non-condensing)

Packaging Dimensions

1133 x 724 x 261 mm

Packaging Content

1 x G291-Z20
1 x CPU heatsinks
1 x Rail kit

Part Numbers

- Barebone with rail kit: 6NG291Z20MR-00-A*
- Motherboard: 9MZ21G20NR-00-2*
- Tool-less rail kit: 25HB2-A86102-K0R
- CPU heatsink for 200W CPU: 25ST1-153104-A8R
- CPU heatsink for 240W CPU: 25ST1-44320G-A0R ( as an option)
- Power supply: 25EP0-222001-D0S
* C19 type power cord 125V/15A (US): 25CP1-018000-Q0R (as an option)
* C19 type power cord 250V/16A (EU): 25CP3-01830H-Q0R (as an option)
- 2 x Internal SSD kit: 6NG291281SR-00 (as an option)

SUPPORT

ملفات للتحميل

برامج تشغيل
BIOS
الأداة
Firmware

دليل المستخدم
قائمة الدعم

Online Support

Choose your OS
Choose your OS
Windows Server 2019
Windows Server 2016 64bit

Chipset

النسخة

الحجم

التاريخ

AMD Chipset Driver

Version : 1.07.12.1102

17.05 MB

2019/08/06

Download

نظام التشغيل: Windows Server 2016 64bit,Windows Server 2019

LAN

النسخة

الحجم

التاريخ

Mellanox LAN Driver

Version : 2.20.50000

31.56 MB

2019/08/19

Download

نظام التشغيل: Windows Server 2016 64bit,Windows Server 2019

VGA

النسخة

الحجم

التاريخ

ASPEED Graphic Driver

Version : 1.06

1.78 MB

2019/08/06

Download

نظام التشغيل: Windows Server 2016 64bit,Windows Server 2019

BIOS

الوصف

النسخة

الحجم

التاريخ

See release note for details

Version : R34_F10

40.54 MB

2021/07/12

Download

Windows and UEFI mode flash BIOS SOP
Please download BIOS update tool from AMI Website

0.39 MB

2021/01/29

Download

Warning:
نظرأ لأ عملية تحديث وحدة التشغيل الرئيسية بها قدر من المخاطرة، نوصي بألا تحاول تحديثها إذا لم تقابلك مشاكل تستدعي ذلك. عند تحديث وحدة التشغيل الرئيسية، تعامل بحرص. التحديث الخاطىء قد ينتج عنه مشاكل في الحاسب

What is a BETA?
النسخة BETA تصف نسخة حديثة وجاهزة للاستخدام إلا أنها قد لا تحتوي على كل الخصائص المتضمنة في النسخة النهائية وتستهدف جمع المعلومات من المستخدمين بما يسهم في الحصول على أفضل تجربة ممكنة

Choose your OS
Choose your OS
Windows Server 2019
Windows Server 2016 R2 64bit
Windows Server 2016 64bit
Windows Server 2012 R2 64bit
Windows Server 2012 64bit
Windows 10 64bit
VMware
Ubuntu
Linux CentOS
Linux

الأداة

الوصف

النسخة

الحجم

التاريخ

GSM CLI

Version : 2.1.44

114.54 MB

2021/03/06

Download

نظام التشغيل: Windows Server 2012 64bit,Windows Server 2012 R2 64bit,Linux CentOS,Windows 10 64bit,Ubuntu,Windows Server 2016 R2 64bit,Windows Server 2019

GSM Server

Version : 2.04

1147.65 MB

2020/12/04

Download

نظام التشغيل: Linux,Windows Server 2016 64bit,Windows Server 2019

BMC Restore Default Setting utility

Version : 1.0

0.15 MB

2020/03/17

Download

نظام التشغيل: Ubuntu

GSM vCenter plugin

Version : 0.05

1856.76 MB

2018/10/08

Download

نظام التشغيل: VMware

GSM Agent

Version : 1.02

671.51 MB

2018/09/21

Download

نظام التشغيل: Linux,Windows Server 2016 64bit,Windows Server 2019

Firmware

الوصف

النسخة

الحجم

التاريخ

BMC Firmware with embedded GIGABYTE Management Console
(AST2500 AMI)

1. ErP Lot9 Supported
2. Guidelines to Preserve Configuration Settings (ErP Lot9 Update)
3. Vertiv BMC EOL & Update Procedure

Version : 12.49.06

94.56 MB

2020/11/29

Download

الانجليزية

BMC Firmware with embedded GIGABYTE Management Console
(AST2500 AMI)

1. Vertiv BMC EOL & Update Procedure
2. Guidelines to Preserve Configuration Settings (ErP Lot9 Update)

Version : 12.40.30

84.21 MB

2020/03/08

Download

الانجليزية

دليل المستخدم

الوصف

النسخة

الحجم

التاريخ

User Guide - GSM Server

Version : 1.2

5.09 MB

2021/02/19

Download

الانجليزية

Hardware Installation Guide

Version : 1.0

15.33 MB

2020/11/13

Download

الانجليزية

User Guide - GIGABYTE Management Console (AMI)

Version : 1.0

15.09 MB

2020/06/10

Download

الانجليزية

User Guide - ErP Mode BIOS Setup

Version : 1.0

0.68 MB

2020/02/26

Download

الانجليزية

User Guide - GIGABYTE GSM Agent

Version : 1.0

1.41 MB

2019/02/19

Download

الانجليزية

User Guide - Easy BIOS Refresh

Version : 1.0

1.45 MB

2017/08/14

Download

الانجليزية

قائمة الدعم

الوصف

النسخة

الحجم

التاريخ

EBrochure_ae

Version : 1.0

0.08 MB

2021/02/04

Download

QVL for G291-Z20 (2021/Q1)

EBrochure_ae

Version : 1.0

0.62 MB

2020/06/12

Download

Datasheet for G291-Z20 (v1.0)

Resources

Insight

Success Case
Articles

Video
News
Media Review
Security & Technical Advisory
Others

Success Case

Articles

Success Case | June 24, 2021

GIGABYTE 5G and Edge Solutions at MWC 2021: The Servers of Choice for Taipei Music Center, ITRI and New Taipei Police, NVIDIA Aerial SDK

GIGABYTE’s E-Series Edge Servers are the highlight of MWC Barcelona 2021. This product line is the fruition of GIGABYTE’s long history of providing 5G and edge computing solutions for key clients, including Taipei Music Center, which wanted to stage VR concerts, and ITRI and New Taipei Police, which needed to maintain order during the Pokémon GO craze. The E251-U70, the first model in the E-Series, exemplifies industry know-how and design philosophy distilled from previous success cases. It has been chosen by NVIDIA to be part of its Aerial Developer Kit.

Success Case | May 31, 2021

Spain’s IFISC Tackles COVID-19, Climate Change with GIGABYTE Servers

By using GIGABYTE, Spain’s Institute for Cross-Disciplinary Physics and Complex Systems is pitting the world’s foremost server solutions against some of the world’s most pressing issues, including the effects of climate change, the effects of pollution, and the COVID-19 pandemic. GIGABYTE servers are up to the diverse and daunting tasks, because they are designed for high performance computing, intensive numerical simulations, AI development, and big data management.

Success Case | April 07, 2021

Lowell Observatory Looks for Habitable Exoplanets with GIGABYTE Servers

Arizona’s Lowell Observatory is studying the Sun with GIGABYTE’s G482-Z50 GPU Server in an effort to filter out “stellar noise” when looking for habitable planets outside of our Solar System. The server’s AMD EPYC™ processors, parallel computing capabilities, excellent scalability, and industry-leading stability are all features that qualify it for this astronomical task, making the discovery of a true “Twin Earth” achievable within our lifetime.

Success Case | October 26, 2020

Decoding the Storm with GIGABYTE’s Computing Cluster

Waseda University, the “Center for Disaster Prevention around the World”, has built a computing cluster with GIGABYTE’s GPU server and tower servers. They use it to study and prepare for natural disasters, such as tsunamis and storm surges. Efforts go into understanding the tropical cyclones of tomorrow, which are thought to become more dangerous due to climate change.

Success Case | September 24, 2020

Constructing the Brain of a Self-Driving Car

GIGABYTE’s High Density Servers Help Technology Innovator Develop Algorithm for Autonomous Vehicle.

Success Case | November 25, 2019

As Good as Gold – High Performance Computing Accelerates Oil Extraction

High Performance Computing (HPC) can complete complex and large-scale computational analysis workloads in a relatively short amount of time, bringing about many breakthroughs in scientific and technological development. HPC is also an indispensable tool for contemporary scientific research, and the number of fields that it can be applied to is constantly growing, such as for weather forecasting, earthquake imaging or genetic analysis. Even oil extraction can now rely on HPC to improve process efficiency and accuracy, allowing mining companies to save a huge amount of money and giving them a greater competitive advantage in the energy market.

Tech Guide | March 16, 2021

How to Pick a Cooling Solution for Your Servers? A Tech Guide by GIGABYTE

As CPUs and GPUs continue to advance, they consume more power and generate more heat. It is vital to keep temperature control in mind when purchasing servers. A good cooling solution keeps things running smoothly without hiking up the energy bill or requiring persistent maintenance. GIGABYTE Technology, an industry leader in high-performance servers, presents this tech guide to help you choose a suitable cooling solution. We analyze three popular options—air, liquid, immersion—and demonstrate what GIGABYTE can do for you.

Advanced | January 09, 2020

[Video] CES 2020 Booth Tour

Our CES booth is luminously lit to disseminate a futuristic aura, and live at the booth are tech demos available for visitors to touch and experience. On the show floor are our product experts providing insights and sharing technology experience. Let's take a look at how you can find your smart innovations in GIGABYTE's solutions!

5G | November 04, 2019

Seize New Business Opportunities with Practical Applications of 5G

Recently, 5G communications technology has been frequently talked about in relation to various major industries – it even seems that in order to keep up with technology trends, everything should be connected with 5G! When discussing 5G however, key features such as high bandwidth, low latency and high connection density must definitely be mentioned. As the coming of 5G will revolutionize our future lives, let’s understand more clearly about 5G directly from some real-world examples! And what key role does GIGABYTE play in this next generation communications technology?

Video

Video | August 09, 2021

GIGABYTE’s servers provide flexibility in selecting high performance computing systems

GIGABYTE's servers provide flexibility in selecting high performance computing systems and better cost-effectiveness, as well as they ensure the reliability and ...

Video | July 28, 2021

Heroes Ascension

Over the past year or so, due to global warming and climate changes, all parts of the world have witnessed extreme weather events that are more severe than ...

Video | July 14, 2021

GIGABYTE Receives ARM SystemReady Trophy

Learn more about GIGABYTE ARM Server Products: https://gbte.tech/7AVl #GIGABYTE #serversolutions #upgradeyourlife #ARM -- Where to buy ...

Video | April 29, 2021

How to Build Your Data Center with GIGABYTE?

Our modern digital age would not be possible without data centers—physical facilities where organizations keep applications and information on a matrix of IT equipment, including computing, storage, and networking devices...

Video | April 12, 2021

Compact GPU Powerhouse: 2U GIGABYTE Server with 8 x GPUs

Designing a 2U server that can accommodate up to 8 dual slot GPUs was a challenge, and the G292-Z40 delivers without sacrificing performance using isolated ...

Video | April 12, 2021

Extreme GPU Powerhouse: 4U GIGABYTE Servers with 10 x GPUs

Showcasing the ultimate in performance for GPU accelerated workloads, the G492-HA0 can house up to 10 high-performing (PCIe Gen 4) GPUs such as the ...

Video | April 08, 2021

List of New GIGABYTE Products for 3rd Gen Intel Xeon Scalable Processors

Intel has made incredible advances with its 40+ SKUs of 3rd Gen Intel Xeon Scalable processors. Higher core count, PCIe 4.0 support with up to 64 lanes per socket, increase in memory bandwidth and total system memory per socket, as well as AI and security boosts have been added while maintaining a competitive price to make these servers an excellent choice for upcoming new sever builds or legacy servers looking to upgrade from prior generations.

Video | March 29, 2021

What is it? Liquid Cooling in 60 seconds

What is Liquid Cooling? As the name suggests, liquid cooling technology uses liquid as a heat transfer mechanism. Two common liquid ...

Video | March 25, 2021

What is it? Data Center in 60 Seconds

What is a data center? A data center is a facility that an organization uses for housing their IT equipment, including servers, storage, ...

Video | March 24, 2021

How to upgrade your system to AMD EPYC 3rd Gen Processors?

If you have a GIGABYTE server designed for AMD EPYC 7002 Series processors, you can painlessly upgrade your system with a BIOS update. On GIGABYTE's ...

Video | March 22, 2021

A Place for All Enterprise Things

Find Your Enterprise Solutions at https://bit.ly/2PfpQ6q This new enterprise homepage will provide easier access for IT professionals and businesses to find ...

Video | March 18, 2021

Ready for our new program "GIGABYTE Tech Tune-In"

Tune in to GIGABYTE'S EXCLUSIVE 'CHANNEL' for webinars, insights, and product solutions on topics of technologies that are transforming the world today.

Video | March 16, 2021

GIGABYTE Launches 1st Wave of Servers for AMD EPYC™ 7003 Series Processors

GIGABYTE servers have been tested and are ready for AMD EPYC 7003 Series processors. The following is a list of models available in the 1st wave ready for ...

Video | March 15, 2021

GIGABYTE Servers and 3rd generation AMD EPYC™ Processors

GIGABYTE announced over 40 servers and server motherboards ready for the new AMD EPYC™ 7003 Series processors. These new servers will target modern ...

News

News | March 22, 2021

Join GIGABYTE at GTC21 to Look at HPC Solutions

News | December 22, 2020

GIGABYTE Joins MLCommons to Accelerate the Machine Learning Community

News | December 04, 2020

Showcasing AMD-Based Solutions and Successes at Annual GIGABYTE-Weikeng Partner Conference

EPYC™ Series Processers Offer Value and Performance, Bringing HPC to Particle Physics, Space Exploration, and Climate Change Studies

News | October 01, 2020

GIGABYTE Showcases Virtual Servers at GTC 2020

News | September 18, 2020

As 9th HPC NCHC 3D Animation Challenge Draws to Close, GIGABYTE Reaffirms Commitment to Tomorrow’s Talent

GIGABYTE GPU Servers Enable Remote Creation, Hybrid Virtual-Real Image Processing, and Digital Asset Library for Taiwan’s Showbiz

Media Review

IT Creations, Inc. | December 17, 2019

GIGABYTE G291-Z20 GPU Server REVIEW

Today we are reviewing another AMD EPYC-powered system! Better yet, this system also supports up to eight dual-slot GPU cards with a single processor. I'm talking about the GIGABYTE G291-Z20 GPU Server, and if you're not very familiar with GIGABYTE products, it's probably because Dell, HPE and Lenovo have been very effective at their brand marketing. Or it means you have not had a need for any High-Performance Computing applications in which GIGABYTE excels. This is a 2U system with a single AMD processor that promises to deliver 2-socket performance for HPC applications in the datacenter. As a single-socket system, the GIGABYTE G291-Z20 GPU server has the potential to save you thousands of dollars while still delivering the goods, thanks to AMD's EPYC processors. What's this system good for? Your basic high-performance computing applications…real-time analytics, scientific simulation and modeling, engineering, visualization and rendering, and… Watch the video!!

Security & Technical Advisory

Security & Technical Advisory | August 20, 2020

BIOS Updates for Security Vulnerabilities: GRUB Bootloader (Boothole) and RowHammer

CVE-2020-10713, CVE-2020-10255

Security & Technical Advisory | March 19, 2020

BMC Unique Pre-Programmed Password Implementation Announcement

N/A

Security & Technical Advisory | March 09, 2020

Important Guidelines to Preserve Configuration Settings When Updating BMC Firmware

N/A

Security & Technical Advisory | March 03, 2020

BMC Firmware Update to Fix Security Vunerabilties in Linux Kernel

CVE-2017-5897, CVE-2019-16994, CVE-2017-18595, CVE-2019-15916, CVE-2017-18509, CVE-2019-9169, CVE-2018-6485, CVE-2018-11236, CVE-2017-15804, CVE-2017-15670, CVE-2018-1000001, CVE-2017-16997, CVE-2014-9761, CVE-2018-15686, CVE-2017-1000253, CVE-2017-8064, CVE-2018-9422, CVE-2018-9568, CVE-2018-1000026, CVE-2017-13305, CVE-2014-7145, CVE-2015-1805, CVE-2014-9529, CVE-2014-7822, CVE-2014-5206, CVE-2014-3631, CVE-2019-10639, CVE-2019-13272, CVE-2016-7910, CVE-2017-2647, CVE-2016-0728

Security & Technical Advisory | February 26, 2020

Compliance with EU Commission Regulation 2019/424 for Energy Efficiency in Server Products (ErP Lot 9)

N/A

Security & Technical Advisory | November 25, 2019

BIOS Updates for GIGABYTE's AMD EPYC "Rome" Server Systems to Fix PCIe Overwrite Error

Rome Erratum 1185

Security & Technical Advisory | July 22, 2019

Statement & Response Plan for Vertiv BMC Firmware Vulnerabilities

CVE-2019-6260, CVE-2018-9086

Security & Technical Advisory | March 26, 2019

ASPEED AST2400 & AST2500 Security Vunerabilities (CVE-2019-6260)

CVE-2019-6260

Others

Micro Sites

Trouble Shooting

Back to G291-Z20