Hello Ceph-Community, we are considering to use a Ceph Cluster for serving VMs. We need goog performance and absolute stability. Regarding Ceph I have a few questions. Presently we use Solaris ZFS Boxes as NFS Storage for VMs. The zfs boxes are totally fast, because they use all free ram for read caches. With arc stats we can see that 90% of all read operations are served from memory. Also read cache in zfs is very intelligent about what blocks to put in the read cache. >From Reading about Ceph it seems that ceph Clusters dont have such an optimized read cache. Do you think we can still perform as well as the solaris boxes ? Next question: I read that in Ceph an OSD is marked invalid, as soon as its journaling disk is invalid. So what should I do ? I don't want to use 1 Journal Disk for each osd. I also dont want to use a journal disk per 4 osds because then I will loose 4 osds if an ssd fails. Using journals on osd Disks i am afraid will be slow. Again I am afraid of slow Ceph performance compared to zfs because zfs supports zil write cache disks . Last Question: Someone told me Ceph Snapshots are slow. Is this true ? I always thought making a snapshot is just moving around some pointers to data. And very last question: What about btrfs, still not recommended ? Thanks for helping Christoph
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