A very low deduplication ratio in a Linux VM farm hosted on an HPE Alletra 9000 could be caused by the use of the XFS filesystem. XFS is known for its performance and scalability but is less effective in environments where deduplication is critical because of its data layout and file handling characteristics. This can lead to reduced deduplication efficiency compared to other filesystems like EXT4 or Btrfs.
For more information, refer to:
* HPE Alletra 9000 Documentation