PowerStore: Possible performance degradation due to multipath configuration as active/active on the host side

Summary: This article describes how performance may be affected by the configuration of host multipath settings as active/active.

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Symptoms

Due to the design of the PowerStore locking mechanisms, if both nodes continuously attempt to get access to the same Logical Block Address (LBA), the primary node controls the access.
This may continue to the point the I/O on the secondary node is starved, and it times out, leading to performance degradation.

An example of both nodes continuously attempting to get access to the same LBA is one node writing to an LBA and the other reading it simultaneously.

Cause

The cause for this issue is a host side path policy set to active/active. This may lead to internode contention of the same LBAs.
PowerStore uses a locking mechanism, that is, only one of two nodes can access the specific LBA simultaneously. If the user configures the host to active/active (A/A) mode, both nodes access the volume and they must lock/unlock the LBA frequently, which would degrade performance.

Resolution

Configure the multipathing settings to ALUA instead of A/A. Doing this allows you to take advantage of the locking by extent as well, which further improves performance.

Affected Products

PowerStore
Article Properties
Article Number: 000130123
Article Type: Solution
Last Modified: 08 Aug 2023
Version:  4
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