As announced in the previous post, I rebooted the blog in order to write about our experiences with OpenStack and Ceph. For the first topic I picked the Ceph cache tiering, as we have recently struggled quite a bit to keep it up and running ;)
We have a lot of short living VMs which are used for automated tests. Those tests are quite IO heavy so we decided to put an NVMe flash based cache tier in front of our regular Ceph pool used for VMs. I’ll post a more detailed overview about our Ceph and OpenStack deployment (and how we arrived there) in future posts, so for now we’ll directly dive into the oddities of Ceph caches.