While we're on this topic, here's some not very technical thought
on load balancing of multipath. When we talk about "load balance",
we always tend to associate it with overall performance improvement
(overall means scalability or throughput of multiple "clients", not
latency of a single "client"). For example, an Oracle cluster
database (called RAC by Oracle) allows more clients to connect to
the database without degraded response time. But here we're dealing
with multipath I/O. It's different in that the work done underneath
is on one single piece of storage hardware, a hard disk (or a
virtual one provided by some storage technology). Because read speed
on the storage itself is always much slower than any of the multi-
paths which is usually fiber channel, whether you have a single or
multiple paths to access the single slow disk will not provide
performance improvement. Am I missing anything obvious?
No doubt multipath provides failover capability or failure
resilience. Even with that one advantage, it's worth it.
Yong Huang
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