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A few notes can be mentioned:

• If Zero-copy limitations – If operating system does not support zero copy, sending a file with FileChannel#transferTo might fail or yield worse performance.
  For example, sending a large file doesn't work well enough on Windows;
• Disbaled SSL connection – SSL must be disabled to take an advantage of Java NIO zero copy file transmission using of FileChannel#transferTo. We can consider to use OpenSSL's non-copying interface to avoid allocating new buffers for each read and write operation at Phase-2;
• Writing WAL io wait time –  Under the heavy load of partition file transmission, WAL-sync operations may slow down. Since the loss of data of temporary WAL storage has no risks we can consider storing the whole storage into memory.

Discussion Links

// Links to discussions on the devlist, if applicable.

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