Windows上的Docker运行缓慢，为什么？

我试图用下面的dockerfile创build一个新的dockerfile ，但是完成其中一个步骤需要很长的时间：

 FROM microsoft/dotnet-framework:4.7 SHELL ["powershell"] # Note: Get MSBuild 12. RUN Invoke-WebRequest "https://download.microsoft.com/download/9/B/B/9BB1309E-1A8F-4A47-A6C5-ECF76672A3B3/BuildTools_Full.exe" -OutFile "$env:TEMP\BuildTools_Full.exe" -UseBasicParsing RUN & "$env:TEMP\BuildTools_Full.exe" /Silent /Full # Todo: delete the BuildTools_Full.exe file in this layer # Note: Add .NET ## RUN Install-WindowsFeature NET-Framework-45-Features ; \ # Note: Add NuGet RUN Invoke-WebRequest "https://dist.nuget.org/win-x86-commandline/latest/nuget.exe" -OutFile "C:\windows\nuget.exe" -UseBasicParsing WORKDIR "C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v12.0" # Note: Add Msbuild to path RUN setx PATH '%PATH%;C:\\Program Files (x86)\\MSBuild\\12.0\\Bin\\msbuild.exe' CMD ["C:\\Program Files (x86)\\MSBuild\\12.0\\Bin\\msbuild.exe"] 

以下是目前的输出：

 PS C:\MyWorkspace\images\msbuild> docker build -t msbuild . Sending build context to Docker daemon 2.56kB Step 1/9 : FROM microsoft/dotnet-framework:4.7 ---> 91abbfdc50cb Step 2/9 : MAINTAINER [e-mail] ---> Using cache ---> fbf720101007 Step 3/9 : SHELL powershell ---> Using cache ---> 642cf0e08730 Step 4/9 : RUN Invoke-WebRequest "https://download.microsoft.com/download/9/B/B/9BB1309E-1A8F-4A47-A6C5-ECF76672A3B3/BuildTools_Full.exe" -OutFile "$env:TEMP\BuildTools_Full.exe" -UseBasicParsing ---> Using cache ---> a722c88fee0f Step 5/9 : RUN & "$env:TEMP\BuildTools_Full.exe" /Silent /Full ---> Using cache ---> 4fda7448f2e4 Step 6/9 : RUN Invoke-WebRequest "https://dist.nuget.org/win-x86-commandline/latest/nuget.exe" -OutFile "C:\windows\nuget.exe" -UseBasicParsing ---> Running in eec036874574 

另外，这里是docker info的输出：

 C:\Windows\system32>docker info Containers: 2 Running: 1 Paused: 0 Stopped: 1 Images: 5 Server Version: 17.06.1-ee-2 Storage Driver: windowsfilter Windows: Logging Driver: json-file Plugins: Volume: local Network: l2bridge l2tunnel nat null overlay transparent Log: awslogs etwlogs fluentd json-file logentries splunk syslog Swarm: inactive Default Isolation: process Kernel Version: 10.0 14393 (14393.1715.amd64fre.rs1_release_inmarket.170906-1810) Operating System: Windows Server 2016 Datacenter OSType: windows Architecture: x86_64 CPUs: 1 Total Memory: 4.75GiB Name: instance-1 ID: B2BG:6AW5:Y32S:YLIO:FE25:WWDO:ZAGQ:CZ3M:S5XM:LSHB:U5GM:VYEM Docker Root Dir: C:\ProgramData\docker Debug Mode (client): false Debug Mode (server): false Registry: https://index.docker.io/v1/ Experimental: false Insecure Registries: 127.0.0.0/8 Live Restore Enabled: false 

什么会导致一个简单的下载步骤永远采取？