【虚拟化实战】存储设计之三MultiPathing

2022-08-07 14:41:18

作者：范军（Frank Fan）新浪微博：@frankfan7 微信：frankfan7

Multipathing 在存储设计中是必须的，因为有多条路径可以访问LUN，它不仅保证了高可用性，同时也有负载均衡的作用。

PSA (PluggableStorage Architecture)

上图是了解Multipathing底层机制的概念。详情参考此文

存储类型

Active-Passive:

在某一时刻仅有一个Storage Processor(SP)拥有对某个LUN访问的专有权。从其他SP对该LUN发起的访问会被拒绝。只有当该主SP失败时，其他的SP对该LUN的访问才会被接受

Active-Active:

没有主SP的概念，某个LUN可以接受任何SP的访问。

MultiPathing策略

基于存储类型，可以参考本文选择相应的Multipathing策略

Policy/Controller	Active/Active	Active/Passive
Most Recently Used	Administrator action is required to fail back after path failure.	Administrator action is required to fail back after path failure.
Fixed	VMkernel resumes using the preferred path when connectivity is restored.	VMkernel attempts to resume using the preferred path. This can cause path thrashing or failure when another SP now owns the LUN.
Round Robin	No fail back.	Next path in round robin scheduling is selected.
Fixed with Array Preference	For ALUA arrays, VMkernel picks the path set to be the preferred path. For both A/A and A/P and ALUA arrays, VMkernel resumes using the preferred path, but only if the path-thrashing avoidance algorithm allows the fail-back.