From 8f27eba7ad58066cd232b566c6fc7228b6cf9385 Mon Sep 17 00:00:00 2001
From: mjkwiatkowski <mati.rewa@gmail.com>
Date: Tue, 7 Jul 2026 14:06:57 +0200
Subject: feat: finished section 2.3

---
 content/background.tex | 70 +++++++++++++++++++++++++++++++++++---------------
 1 file changed, 49 insertions(+), 21 deletions(-)

(limited to 'content/background.tex')

diff --git a/content/background.tex b/content/background.tex
index 03f06cb..ab361f2 100644
--- a/content/background.tex
+++ b/content/background.tex
@@ -4,9 +4,10 @@
 
 \section{Datacenters}\label{ss:datacenters}
 
-\subsection{Computing Infrastructure}\label{sss:failures}
-
 \subsection{Datacenter Simulation}\label{sss:simulation}
+\input{sources/simulator_comparison.tex}
+
+\subsection{Hardware Failures}\label{sss:failures}
 
 Predictive modelling uses statistics to predict outcomes.
 When deployed commercially, for example in datacenters, predictive modelling is often referred to as predictive analytics~\cite{Wikipedia:PredictiveModelling}.
@@ -22,7 +23,6 @@ A prime example of using probability to find a good machine learning model is Ba
 % Stanford Encyclopedia of Philosophy, Douven 2017
 The process of inference from data to provide the best explanation is called abduction.
 
-
 %What is below here is true, but nonetheless the argumentation should be slightly changed. And a citation is needed.
 However, there has been little effort made to integrate analytics that enable consistent and reliable prediction of datacenter behaviour into a holistic digital twin of a datacenter.
 Nor has the fidelity of failure modeling inside a datacenter simulation increased.
@@ -31,9 +31,6 @@ Since a datacenter simulator is quite different from a digital twin, we cannot u
 The prediciton models are the same ones for the digital twin as the ones used for the datacenter simulator.
 Since a digital twin is not a standalone simulator, a change to how we both predict and model failures is necessary.
 
-\ipsum[1-2]
-
-\input{sources/simulator_comparison.tex}
 \section{Digital Twinning}\label{ss:digital-twinning}
 % To fix: remove the \gls commands for ExaDigiT.
 % This is getting silly.
@@ -60,7 +57,7 @@ As a result, digital twins have become more relevant today than 10 years ago~\ci
 \end{figure}
 % (3) in the original paper by Fei Tao is referenced to just `Services`.
 % Nonetheless I name them here as Data Analysis Services, because what Fei Tao lists (e.g., fault detection, fault determination, fault-tolerant management, maintenance) is inherently reliant on good data analytics.
-\subsection{Digital Twins across Domains}\label{sss:digital_twins_across_domains}
+%\subsection{Digital Twins across Domains}\label{sss:digital_twins_across_domains}
 
 \subsection{Digital Twins for Datacenters}\label{sss:digital_twins_for_datacenters}
 
@@ -104,13 +101,51 @@ The digital twin is designed to provide extra datasets for training \gls{ai} mod
 % At this point it would make sense to create the distinction between _structural_ digital twinning and _behavioural_ digital twinning.
 % Link to 6SigmaDC: https://www5.cadence.com/trial_datacenter_insights_lp.html
 
+\begin{figure}[t]
+	\centering
+	\includegraphics[width=\linewidth]{images/system_model.pdf}
+	\caption{A generic system model for data center digital twin deployments.
+		The design of DyTwin~\cite{DBLP:conf/sc/TaheriBPRHDEWPM24}  indirectly incorporates in its architecture a ``virtual-to-virtual`` digital thread between different digital twins.
+		Zhao \etal likewise present key elements to the digital thread in their architecture~\cite{DBLP:conf/AppliedEnergy/Zhao20}. We add the \emph{Digital Thread} to our model explicitly.}
+	\label{fig:system_model}
+\end{figure}
+
 DyTwin~\cite{DBLP:conf/sc/TaheriBPRHDEWPM24} is an adaptive digital twin with visualization and anomaly detection features.
+The system, developed at \gls{hp} is a precursor to the vision on datacenter digital twinning published by Athavale \etal~\cite{DBLP:journals/computer/AthavaleBBMMPS24}.
+DyTwin is the only system capable of failure detection in datacenters.
+Moreover, it is the only system to incorporate the idea of federation into the concept of digital twinning.
+DyTwin is designed to interact not only with the physical facility, but also other federated digital twins.
+Taheri \etal show that DyTwin can effectively detect 100\% of CPU usage anomalies (\ie irregularities that affect CPU utilization, ranging from 5\% to 60\%).
+
+ChatTwin~\cite{DBLP:conf/sensys/LiW0Z0T23} is an \gls{ai} and \gls{llm} powered system that enables easy deployment and configuration of digital twins for datacenters.
+It is a \emph{text-to-3D} approach to building digital twins of datacenters.
+ChatTwin is the only work in the field that does not share the simulation technique used to construct the digital twin based on ChatTwin's configuration.
+Li \etal provide a thorough set of experiments to show ChatTwin generates the \gls{json} \gls{dcdt} configuration efficiently, but do not share the final 3D visualization results.
+
+Reducio~\cite{DBLP:conf/sensys/CaoW0022} is a system designed to further optimize the \gls{cfd} approach to datacenter modeling.
+Instead of using plain \gls{cfd} the authors focus on \gls{pod} approaches to approximate the heat transfer.
+Using the \gls{pod} technique, the authors are able to model the datacenter more efficiently, achieving sub 1 degree Celsius \gls{mae} in temperature prediction.
+Moreover, their model outperforms the \gls{cfd} approaches.
+Cao \etal evaluate their system on an edge datacenter with 70 CPU-only server racks (see Figure 3 in \cite{DBLP:conf/sensys/CaoW0022}), and on a hyper-scale datacenter with thousands of servers (see Figure 4 in \cite{DBLP:conf/sensys/CaoW0022}).
+Their results show promising gains in physics-based datacenter modelling over the conventional approaches.
+
+NetGraph~\cite{DBLP:conf/sigcomm/HongWDSSHZY21}, designed by Huawei Technologies and China Mobile.
+NetGraph is the only system in our literature review that focuses on network management (see \Cref{tab:dt_features_comparison}).
+Moreover, NetGraph employs a unique modelling technique, combining device, network and service models using graph theory.
+The authors evaluate their system in a Huawei datacenter with over 50000 server racks.
+With over 20 million connections in the network graphs, the system is a prime example of datacenter digital twin potential.
+
+Kalibre~\cite{DBLP:conf/sensys/WangZD0TCWZ20} is a system designed by Wang \etal in order to overcome the cons of \gls{cfd}.
+To lessen the computational overhead, Wang \etal propose to use a knowledge-based neural surrogate to calibrate the different \gls{cfd} models.
+Kalibre takes the best of both \gls{ml} and \gls{cfd} approaches and achieves sub 1 degree Celsius \gls{mae}, similarly to Reducio~\cite{DBLP:conf/sensys/CaoW0022}.
+
+
 
 % What is more, Microsoft already offers digital twinning as a service https://azure.microsoft.com/en-us/products/digital-twins/
 % Documentation: https://learn.microsoft.com/en-us/azure/digital-twins/
 % Moreover, NVIDIA is doing too as well https://www.nvidia.com/en-sg/omniverse/
 
-Many \gls{dcdt}'s model the cooling systems inside the warehouse, because in a typical datacenter cooling accounts for more than 40\% of total electricity usage~\cite{DBLP:conf/AppliedEnergy/Zhao20}.
+To summarize, many \gls{dcdt}'s model the cooling systems inside the warehouse, because in a typical datacenter cooling accounts for more than 40\% of total electricity usage~\cite{DBLP:conf/AppliedEnergy/Zhao20}.
 Since the cooling subsystem is mainly airflow-based, \gls{dt} designers often opt for a \gls{cfd} approach to model the facility.
 The reason why a digital twin might be needed for a cooling subsystem is primarily because of inefficient operational strategy.
 The cooling system parameters are often set constant, regardless of outdoor temperature \etc~\cite{DBLP:conf/AppliedEnergy/Zhao20}.
@@ -119,26 +154,19 @@ The cooling system parameters are often set constant, regardless of outdoor temp
 % Zhang argues that ``digital twin services'' are enabled by simulation monitoring \etc.
 % Nonetheless, I dub that they are primarily data analysis services.
 
-\gls{oda} can be performed in-band (real-time) and out-of-band (from historical data).
-Likewise, Zhao \etal shows that crucial to the digital twin system are ``always-on'' analytics (akin to in-band \gls{oda}) and ``on-demand`` analytics (akin to out-of-band \gls{oda}).
+%\gls{oda} can be performed in-band (real-time) and out-of-band (from historical data).
+%Likewise, Zhao \etal shows that crucial to the digital twin system are ``always-on'' analytics (akin to in-band \gls{oda}) and ``on-demand`` analytics (akin to out-of-band \gls{oda}).
 
 %Include something about data-preprocessing in the pipeline.
 %See the article by Fei Tao
 
-\begin{figure}
-	\centering
-	\includegraphics[width=0.7\linewidth]{images/system_model.pdf}
-	\caption{A generic system model for data center digital twin deployments.}
-	\label{fig:system_model}
-\end{figure}
-
-The design of DyTwin~\cite{DBLP:conf/sc/TaheriBPRHDEWPM24}  incorporates in its architecture a ``virtual-to-virtual`` digital thread between different digital twins.
-Zhao \etal include this element in their architecture too~\cite{DBLP:conf/AppliedEnergy/Zhao20}.
-Moreover, a crucial parallel between the work of Zhao \etal and ExaDigiT is the concept of multiple models within a single digital twin.
-Brewer \etal argue ExaDigiT is compromised of 5 ``smaller'' twins too.
 
+%Moreover, a crucial parallel between the work of Zhao \etal and ExaDigiT is the concept of multiple models within a single digital twin.
+%Brewer \etal argue ExaDigiT is compromised of 5 ``smaller'' twins too.
 %In Zhang \etal the digital twin can communicate with different other digital twins, as in the work of Taheri \etal.
 %To do this, the working program has an API, with a specific API endpoint to communicate with other Digital Twins.
+
+
 %In your work, consider adding such an endpoint, albeit explain in future work that you envision \emph{implementing} this endpoint in the future.
 
 
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