ISSUE
Backups are failing due to out of space on NAS (e.g. Data Buffalo Terastation NAS or Synology)
The device is using a recycle bin/trash where deleted files are being sent but never completely removed.
Note, this issue will only occur if you are using CIFS/NFS connection to NAS devices otherwise not listed as supported devices in KB 3350.
Though Unitrends will make a "best effort" review to identify issues with storage vendors not certified by our QA department, Unitrends Support may limit troubleshooting of such configurations and may insist on redeployment in an officially supported configuration if performance or other issues persist.
RESOLUTION
To avoid this issue entirely, follow Unitrends Best Practice per Deployment Guide recommendations and KB 3085 , doing the following:
1) Deploy UB on storage devices openly supported by your hypervisor vendor for production VM deployment. See your Hypervisor vendor's supported storage web page to confirm supported hardware models and connection methods.
2) Always connect your external storage to your hypervisor as a datastore instead of using passthru storage. iSCSI is the preferred connection method for most providers and almost every NAS device sold supports this method. CIFS/NFS host-level datastores should be a last resort only given inferior performance they provide.
3) Connect virtual disks to your UB in your configured datastore and expand the "internal" storage device to grow to use all configured storage. Remember, never connect storage residing in multiple separate storage devices to a single UB, deploy multiple UBs instead if a single storage system cannot accomodate all your UB storage. Multiple datastores in the same physical device are supported.
4) for NAS systems that cannot provide at least 500 sustained write IOPS, review moving your Unitrends database engine to alternate high performance virtual disks using
KB 4461 or use a Dedupe level 1.
To resolve this issue on a system already deployed that cannot be redeployed to best practices, follow the below instructions.
You must disable the use of Recycle Bin/TRASHBOX in your NAS, as it is not supported.
For Synology, to disable Recycle Bin:
1) Control Panel
2) Select File Sharing > Shared Folder
3) Right Click the icon of the folder
4) Select Edit
5) Uncheck the Enable Recycle Bin
To get rid of the TrashBox on the Terastation, disable the Recycle Bin option in the Shared Folder. This should delete the TRASHBOX. This may take time depending on the amount of data in the directory. Check with Buffalo to verify it is OK to delete this directory after disabling the Recycle Bin.
CAUSE
The use of the Recycle Bin or TRASHBOX causes conflicts in the amount of data that is free on the NAS, and the purging process expected because deleted data is not removed from the volume until additional user manual steps are taken. Data deleted by Unitrends must be removed entirely from the NAS. No other data may share the same logical volume Unitrends used for backup storage.
Check the datastore using a Windows system. If you see a TRASHBOX, then your NAS has the Recycle Bin enabled. This is not an acceptable configuration with the Unitrends solutions, as the NAS can not purge the data in the Recycle Bin because it also can not report the proper space to the Unitrends Systems (Linux).
NOTES
Buffalo: http://sg.faq.buffalo-global.com/app/answers/detail/a_id/14207/p/31,32,515,518
Synology: https://www.synology.com/en-us/knowledgebase/DSM/help/DSM/AdminCenter/file_share_recycle