IBM Aspera HST Admin Manual page 219

• Utilizes high-speed Aspera FASP transport for moving data at maximum speed over the WAN, whereas traditional
synchronization tools are built on TCP. Aspera Sync transfers new data between remote hosts at full bandwidth
capacity, regardless of round-trip delay and packet loss, and does not degrade in performance for large file sizes.
• Compares against a local snapshot, thereby avoiding making a comparison against the remote file system over the
WAN, which is used by most traditional tools and can be slow.
• Recognizes file system changes (such as moves and renames) on the source and propagates these changes to the
destination. Traditional tools treat these operations as deletion of old data and then recreate or re-transfer the new
data, which can lead to costly data copying over the WAN.
• Supports bi-directional and multi-directional synchronization topologies, where files are changing on multiple
nodes. For a bi-directional synchronization, Aspera Sync runs with a bi-directional option. For a multi-directional
synchronization, one session is run for each peer to remain sync. Any topology that has an acyclic graph topology
between peers is supported.
• Uses file system notifications for change notification, when available.
• Monitors file contents and waits for files to be stable (no longer changing in md5sum) before transferring. The
wait period is configurable and is designed to avoid transferring only partially complete files.
Aspera Sync is a command-line tool, async, that uses an SSH connection to establish connectivity with its remote
peers and is spawned as an SSH subsystem binary on the remote system. The program can be run one time or
periodically (through a cron tab scheduled job) on file systems that do not provide asynchronous change notification,
or in a continuous mode on file systems that do support asynchronous change notification. Aspera Sync is designed
to process files and transfer new data in a continuous pipeline for maximum speed, even when running in scan-only
mode (when no file system change notification is available).
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