No Space for Snapshot

[Pi-L]

I bet adding some space to temp unit could help.
And if you are in a position without any spare hdd left you can create iSCSI target on your real unit and connect to it from temp unit initiator and create snapshot volume.

[aldoscic]

I know i could add an extra drive and increase the size of my array, but i do not want to risk this data. What i will probably do is use a replication program from my workstation and copy the data across, then i test your suggestion on the temp unit.

Thanks for the suggestion

[Al-S]

DSS System save 4GB of SWAP at "System Volumes", you can delete it to free some space.