Usage of Regular Expressions (regexes) to identify devices is not recommended for use in /etc/mulitpath.conf
This document (7018191) is provided subject to the disclaimer at the end of this document.
SUSE Linux Enterprise Server 11 Service Pack 4 (SLES 11 SP4)
The following is an example of how to properly specify a DGC VRAID device with a custom hardware handler setting in /etc/multipath.conf:
hardware_handler "1 alua"
features "1 queue_if_no_path"
hardware_handler "1 emc"
When a new device is added to multipath a regular expression match will be done between the incoming "vendor" and "product" strings against those in the built-in hardware table to determine if the incoming device matches this entry. If an /etc/multipath.conf file is created, the intention of this configuration file is to override or add to the built-in hardware table.
If the configuration from /etc/multipath.conf were to be read first, all settings from later configurations for a device will be lost requiring the user to specify the device with all its relevant entries. This means that any default settings specified by the built-in hardware table will be lost, especially updates to settings from the build-in hardware table would not be reflected in the custom settings, which can result in degraded performance and/or invalid custom settings after updates.
If the configuration from /etc/multipath.conf is checked after parsing the internal hardware table, it is needed to determine where the updated settings should be applied. This would require calculating the overlap of two different regular expressions, and modify the original regular expression from the internal hardware table to exclude the overlap region which can potentially be unsolvable as the required computation increases exponentially.
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- Document ID:7018191
- Creation Date: 26-Oct-2016
- Modified Date:03-Mar-2020
- SUSE Linux Enterprise Server
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