anchor.diff:  Disks use the same network as the VMs so you start running into the Azure limits in bigger clusters when using big virtual machines with 32 disks on each one.  The overall throughput drops as you hit this limit and is most noticeable during concurrency testing.
   
   ### <a id="az-recommend"></a>Azure Recommendations
  -The best instance type to use in Azure is "Standard_H16" which is one of their High Performance Compute instance types.  This instance series is the only one utilizing InfiniBand, but this does not include IP traffic.
  +The best instance type to use in Azure is "Standard_H8" which is one of the High Performance Compute instance types.  This instance series is the only one utilizing InfiniBand, but this does not include IP traffic. Because this instance type is n0t available in all regions, the "Standard_D13_v2" is also available.
   
  +##### Master
  +| Instance Type | Memory | vCPUs | Data Disks |
  +| ------------- | ------ | ----- | ---------- |
  +| D13_v2        | 56     | 8     | 1          |
  +| H8            | 56     | 8     | 1          |
   
  -| Instance Type             | Storage Type | Storage Size      | Memory | vCPUs<sup>3</sup> | Use                   | Notes                    |
  -|---------------------------|--------------|-------------------|--------|-------------------|-----------------------|--------------------------|
  -| Standard_D14_v2           | HDD          | 8x2TB<sup>2</sup> | 112    | 16                | Dev/Test - Production | Use if HPC not available |
  -| Standard_H8<sup>1</sup>   | HDD          | 4x2TB<sup>2</sup> | 56     | 8                 | Dev/Test - Production |                          |
  -| Standard_H16<sup>1</sup> | HDD          | 8x2TB<sup>2</sup> | 112    | 16                | Dev/Test - Production | Fastest                  |
  +##### Segments
  +| Instance Type | Memory | vCPUs | Data Disks |
  +| ------------- | ------ | ----- | ---------- |
  +| D13_v2        | 56     | 8     | 2          |
  +| H8            | 56     | 8     | 2          |
   
  -<sup>1</sup> Not all regions have HPC instance types.
  -
  -<sup>2</sup> Use 2 disks in each RAID 0 volume.
  -
  -<sup>3</sup> Some, but not all, Azure VMs have hyperthreading. If hyperthreading is not enabled, 1 vCPU = 1 Core.
  -
  
positive.code: 
  The HighMem instance type is slightly faster for higher concurrency.  Furthermore, SSD disks are slightly faster also but come at a cost.
  
  | Instance Type | Storage Type | Storage Size | Memory | vCPUs | Network Speed | Use                                    |
  |---------------|--------------|--------------|--------|-------|---------------|----------------------------------------|
  | n1-standard-8 | HDD          | 6TB or 3TB   | 30     | 8     | 10Gbit        | Dev/Test - Production                  |
  | n1-standard-8 | SSD          | 1.4TB        | 30     | 8     | 10Gbit        | Dev/Test - Production                  |
  | n1-highmem-8  | HDD          | 6TB or 3TB   | 52     | 8     | 10Gbit        | Dev/Test - Production                  |
  | n1-highmem-8  | SSD          | 1.4TB        | 52     | 8     | 10Gbit        | Dev/Test - Production High Concurrency |
  
  ## <a id="azure"></a>Azure
  
  
negative.code:    ```
      <br/>**Note:** The `nobarrier` option is not supported on Ubuntu nodes.
  -  Use mq-deadline instead of the deadline scheduler for the R5 series instance type in AWS
  -  Use a swap disk per VM (32GB size works well)
  
  ## <a id="cd-security"></a>Security
  
  It is highly encouraged to disable SSH password authentication to the virtual machines in the cloud and use SSH keys instead.  Using MD5-encrypted passwords for Greenplum Database is also a good practice.
  
  ## <a id="aws"></a>Amazon Web Services (AWS)
  
  ### <a id="aws-vm-type"></a>Virtual Machine Type
  AWS provides a wide variety of virtual machine types and sizes to address virtually every use case.  Testing in AWS has found that the optimal instance types for Greenplum are "Memory Optimized".  These provide the ideal balance of Price, Memory, Network, and Storage throughput, and Compute capabilities.
  
  Price, Memory, and number of cores typically increase in a linear fashion, but the network speed and disk throughput limits do not.  You may be tempted to use the largest instance type to get the highest network and disk speed possible per VM, but better overall performance for the same spend on compute resources can be obtained by using more VMs that are smaller in size.
  
  #### <a id="aws-compute"></a>Compute
  AWS uses Hyperthreading when reporting the number of vCPUs, therefore 2 vCPUs equates to 1 Core.  The processor types are frequently getting faster so using the latest instance type will be not only faster, but usually less expensive.  For example, the R5 series provides faster cores at a lower cost compared to R4.
  