We just enabled a small cache pool on one of our clusters (v 0.94.1) and
have run into some issues:
1) Cache population appears to happen via the public network (not the
cluster network). We're seeing basically no traffic on the cluster
network, and multiple gigabits inbound to our cache OSDs. Normal
rebuild/recovery happens via the cluster network, so I don't believe
this is just a configuration issue.
2) Similar to #1, I was expecting to see cache traffic show up as repair
traffic in 'ceph status'. Instead, it seems to appear as a client traffic.
3) We're using a readonly pool (we only really write to our pools
once). I noticed that if all the OSDs hosting the cache pool go down,
all reads stop until they're restored. I would have expected that reads
would fall back to the backing pool if the cache pool is unavailable.
Is this how it's supposed to work?
Any thoughts on these? Are my expectations just wrong here? The
documentation is fairly sparse, so I'm not quite sure what to expect.
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