Multipath I/O stats

Yong Huang yong321 at yahoo.com
Sat May 22 17:28:12 UTC 2010


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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