Hi,

 

I’m using Ceph in combination with Openstack. For the “VMs” Pool I’d like to enable writeback caching tier, like described here: https://docs.ceph.com/docs/luminous/rados/operations/cache-tiering/ .

 

Can you explain why? The cache tiering has some serious flaws and can even decrease performance instead of improve it.

What are you trying to solve?

Wido

Should it be possible to do that on a running pool? I tried to do so and immediately all VMs (Linux Ubuntu OS) running on Ceph disks got readonly filesystems. No errors were shown in ceph (but also no traffic arrived after enabling the cache tier). Removing the cache tier , rebooting the VMs and doing a filesystemcheck repaired everything.

 

Best

Robert

 

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