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OceanStor UltraPath for vSphere 21.3.0 User Guide 03

This document covers the functions, features, installation, configuration, upgrade, uninstallation, maintenance, troubleshooting, and FAQs of OceanStor UltraPath for vSphere (UltraPath forvSphere). UltraPath for vSphere is the multipathing software developed by HuaweiTechnologies Co., Ltd (Huawei for short). The document aims at helping users to be fully familiar with UltraPath for vSphere and its use.
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Timeout Parameter Settings upon a Link Down Failure

Timeout Parameter Settings upon a Link Down Failure

This chapter describes how to set the timeout parameters upon a link down failure of an iSCSI initiator and some mainstream HBAs.

A link down failure triggers an I/O failover. This is a common fault mode. Under this condition, the time for the I/O failover consists of two parts: time for an initiator to sense the link down failure and timeout period of the link down failure of the initiator.

  • Time for an initiator to sense a link down failure indicates a period from the physical link down failure to the initiator's identification of the link down failure. This period varies based on different initiator hardware, driver versions, networks, and physical fault locations. Generally, FC HBAs sense a link down failure faster than an iSCSI initiator does. The speed for sensing a link down failure accelerates when the fault location is close to a host.
  • The timeout period of a link down failure of an initiator indicates a period from the initiator's identification of the link down failure to I/O queue suspension. (After I/Os are suspended, the initiator returns I/Os that have the link down error code to UltraPath. UltraPath immediately switches I/O services to a standby path.) This timeout period depends on the timeout parameters of the initiator. You can control the time for an I/O failover by modifying the timeout parameters.

Typically, you can use the default timeout parameter configuration of an initiator upon a link down failure. However, some application services has special requirements on I/O latency. For example, Oracle RAC requires short I/O latency. Under this condition, you can set a short timeout period upon a link down failure. The timeout parameter value varies based on different service environments. If services have special requirements on an I/O failover, you are advised to set the timeout parameters based on the actual environment.

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Updated: 2019-06-29

Document ID: EDOC1100052672

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