Do monitors have any impact on read/write latencies? Everything I've read says no, but since a client needs to talk to a monitor before reading or writing to OSDs it would seem like that would introduce some overhead.
I ask for two reasons:
1) We are currently using SSD based OSD nodes for our RBD pools. These nodes are connected to our hypervisors over 10Gbit links for VM block devices. The rest of the cluster is on 1Gbit links, so the RBD nodes contact the monitors across 1Gbit instead of 1Gbit. I'm not sure if this would degrade performance at all.
2) In a multi-datacenter cluster a client may end up contacting a monitor located in a remote location (e.g., over a high latency WAN link). I would think the client would have to wait for a response from the monitor before beginning read/write operations on the local OSDs.
I'm not sure exactly what the monitor interactions are. Do clients only pull the cluster map from the monitors (then ping it occasionally for updates), or do clients talk to the monitors any time they write a new object to determine what placement group / OSDs to write to or read from?
Thank You,
Logan Barfield
Tranquil Hosting
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