Azure Site Recovery (ASR) uses storage accounts for various purposes during replication, and the usage of cache storage accounts depends on the source and target platforms you are working with.
Here is a brief overview of ASR storage account usage for different scenarios:
- Azure VMs replicating to another Azure region: In this case, ASR uses a cache storage account in the source region to store the replication data before it gets transmitted to the target region.
- On-premises VMs replicating to Azure: ASR uses a Process Server, which is an on-premises component, to cache, optimize, and encrypt the replication data. In this scenario, there's no cache storage account involved in Azure. The data is directly written to the main storage account in the target region.
- VMware VMs or physical servers replicating to Azure: ASR uses a Configuration Server and Process Server running on-premises. The Process Server caches the replication data, optimizes, and encrypts it before sending it to Azure. Similar to the on-premises VMs scenario, there's no cache storage account involved in Azure.
In summary, the cache storage account in Azure is used only when replicating Azure VMs to another Azure region. The size of the cache storage account will depend on the change rate of your VMs and the retention period configured for your replicated data.
If you observe that the cache storage account is growing more than expected, you might want to verify that the storage account is indeed being used as a cache for ASR, and not for any other unrelated purposes. Additionally, check your replication settings to ensure the retention period and other configurations are as intended.