From where the high cache usage is coming?

[RichardIstSauer]

Hello after around two days my cache runs out of space. And I have no idea what it could be. The cache are two 120GB SDD's which are connected to a PCI-E SATA Card JMB363 and run RIAD 1 btrfs. I hope someone can help me ^^.

 

Full Cache:

 

 

Then I run the btrfs defragmentation (btrfs filesystem defragment -rvf /mnt/cache) and all is good for the next two days.

 

Two more screenshots:

 

Before defragmentation:                                                                                                        

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After defragmentation:

Edited November 25, 2021 by RichardIstSauer

[JorgeB]

In the first screenshot there's still plenty of space, but if the free space keeps getting lower without writing new files it's usually lack of discard on vdisks, see here for Windows VMs:

https://forums.unraid.net/topic/51703-vm-faq/?do=findComment&comment=557606

 

[RichardIstSauer]

5 hours ago, JorgeB said:

but if the free space keeps getting lower without writing new files

Yes the data grow's around 100MB per hour.

 

5 hours ago, JorgeB said:

usually lack of discard on vdisks, see here for Windows VMs

The only VM I use is based on Qcow2 Home Assistant Image. Could this be the cause for the growing cache space usage?

 

[JorgeB]

Any vdisk that doesn't discard freed space will keep growing.

[RichardIstSauer]

I added the discard parameter and the fstrim linux service at the vm. But it not changed so much. I had an disk usage at 90GB then I started the fstrim service manually and then only 80GB were used. But that also was too much so I ran the btrfs defragmentation "btrfs filesystem defragment -rvf /mnt/cache" and then the disk usage was only 64GB.