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Reclaim free space xenserver 7.6

scott budworth


Hi, Guys!. 


i know this has been asked over and over but i cant find any information relevnt to xenserver 7.6


i have deleted old snapshots but the space has not been reclaimed by the system, should be aprox 2TB free'd up from snapshots. 


reclaimed space doesnt work on this version and i checked i have a LVM filesystem so colance should be running automaticly. 


4060.3 GB used of 5538.5 GB total (19920 GB allocated)


can anyone help me figure this out please?

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Aside from XenServer 7.6 being long since End of Life.


With 1.5TB free you should have plenty of spare space to permit the coalesce (it temporarily requires extra space whilst running in order to combine the active data blocks), which means that you shouldn't be hitting the most common reason which is that lack of space. The other very common case is that the coalesce of the final part of the snapshot tree cannot be completed as the VM is writing data to the leaf node faster than the coalesce process can merge things into the parent node. This can result in each VM taking 2x the amount of space assigned to it, the leaf node is always fully committed to the size assigned to allow the VM to write wherever it needs to and if the parent node is full of data and/or dirty data blocks then it can be the same size (or very close to).


There have been some improvements in this area in Citrix Hypervisor 8.2, notably a dynamic limit control on when the leaf coalesce decides to pause the VM for the final offline coalesce, this helps in a lot of cases but is not completely guaranteed to complete if the VM is very busy performing writes.

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if the VM is wriring data fast, how long should i shut it down for to complete the process? - Tried shutting down the VM for a while, no avail. 


also attempted to process mahually: 

 xe host-call-plugin host-uuid=c57163c2-c1b0-43ab-b5ce-0c61d587d8dc plugin=coalesce-leaf fn=leaf-coalesce args:vm_uuid=76668f62-94eb-f32d-b1b1-ab48426769a1
VM has no leaf-coalesceable VDIs

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I'm 80-90% sure it's not that there insufficient space in the SR (there is 1.5TB free). It's much more likely IMO that it's the GC not keeping up with the VM write. I can't remember what the log looks like in 7.6 when the GC gives up but there's probably something in /var/log/SMlog to give a hint.

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