Data Transfer Methods
Upgrade is made possible by specific capabilities in version 2 and version 3 called Upgrade: Agent and Upgrade. These capabilities manage the communication between the two servers and can transfer all configuration via web protocols. The bulk of the data to be transferred consists of all the binary components in the repositories that are upgraded. Once the Upgrade: Agent and Upgrade capability, mentioned in Starting the Upgrade, is enabled and both repository manager instances are communicating, you can choose one of three methods for this transfer:
When running the HTTP download method, we discourage you from synchronizing repository manager content to cloud services or on-premises data centers. This tool is solely designed to allow for data and configuration transfers between Nexus Repository Manager 2 to 3.
HTTP download is a transfer method in which version 3 makes HTTP requests to version 2 to transfer configuration and data. This is the slowest option.
If version 2 and version 3 are running on different machines and do not share access to the same file system storage, you must use the HTTP download method.
File System Copying
In this transfer method, version 2 tells version 3 the path of the file content to transfer and a simple file system copying is performed.
This upgrade method works if versions 2 and version 3 are configured to access the same storage system on identically named mount points. It is a faster process than the HTTP Download method, and has less impact on the performance of version 2.
File System Hard Linking
In this transfer method, version 2 tells version 3 the path of the file content to transfer and a file system hard link to the same content is created.
This upgrade method works if versions 2 and version 3 are configured to access the same storage system on identically named mount points and hard linking is supported by the file system used. It is the fastest transfer method.
File System Considerations
While discussed in greater detail in Blob Stores, Nexus Repository Manager 3 allows you to create and name multiple blob stores to store your content. Before you start the upgrade process it is important to consider how you want to allocate space within the storage system.
When upgrading, make sure you have enough storage capacity in the destination file system(s). For instance, if you are using hard linking, the data is not duplicated. This saves storage space, but you must ensure that there are enough file handlers available for the content you want to transfer during the upgrade process. On the other hand, file copy and downloading do duplicate your data so upwards of double the original storage space can be, at least temporarily, needed.