General availability: New Azure Batch capabilities

Use Azure Batch to run large-scale parallel and high-performance computing (HPC) batch jobs in Azure. The following new Batch features are now available. **Pool Managed Identities** User-assigned managed identities [can be associated with Batch pools](https://docs.microsoft.com/azure/batch/managed-identity-pools) so the pool nodes can then use the identity to access Azure resources. The managed identity can also be used to access Azure resources specifically supported by Batch, such as resource files. **Pool Virtual Machine Extensions** Specific [virtual machine extensions](https://docs.microsoft.com/azure/virtual-machines/extensions/overview) can be [associated with Batch pools](https://docs.microsoft.com/azure/batch/create-pool-extensions), with the specified extensions being installed on each pool node. **Pool Availability Zone Support** [A pool can now be configured](https://docs.microsoft.com/rest/api/batchservice/pool/add#nodeplacementpolicytype) to allocate pool nodes across all the availability zones where the pool VM size is available and in a region that supports availability zones. **Pool Node Ephemeral OS Disk Support** Some VM series support [ephemeral OS disk](https://docs.microsoft.com/azure/virtual-machines/ephemeral-os-disks) where the OS disk is created on local VM storage instead of remote Azure Storage. For supported VM sizes, [Batch pools can now specify ephemeral OS disk is used](https://docs.microsoft.com/rest/api/batchservice/pool/add#osdisk) for the pool nodes. **Exact Marketplace VM Image Version** The specific version of the platform image or marketplace image used to create the node [is now available for a pool](https://docs.microsoft.com/rest/api/batchservice/compute-node/get#imagereference). **List Supported VM Sizes** It is now possible to list (via API, CLI and Powershell) the VM sizes supported by Batch for both [Cloud Service](https://docs.microsoft.com/rest/api/batchmanagement/location/list-supported-cloud-service-skus) and [Virtual Machine](https://docs.microsoft.com/rest/api/batchmanagement/location/list-supported-virtual-machine-skus) pools. **Account Authentication Control** The service API authentication mechanism for a Batch account can be restricted to only Azure Active Directory using the ‘[allowedAuthenticationModes](https://docs.microsoft.com/rest/api/batchmanagement/batch-account/create#batchaccount)’ property; API calls using access key authentication will be rejected. **Application Limit** The maximum number of applications for a Batch account has been increased from 20 to 200. For information about all Batch updates see the [service REST API](https://docs.microsoft.com/rest/api/batchservice/batch-service-rest-api-versioning) and [management REST API versioning](https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/batch/Microsoft.Azure.Management.Batch/CHANGELOG.md#1400-2021-08-01) documentation. * Batch * Features * [ Batch](https://azure.microsoft.com/en-gb/services/batch/)