What is a specific configuration guideline that should be followed when configuring Linux hosts to support XtremIO storage?

For optimal performance with Linux hosts, Dell EMC recommends tuning the LUN queue depth. Setting the queue depth to 64 for XtremIO devices allows the host to send a sufficient number of concurrent I/O requests to the array. This ensures that the high-performance, low-latency capabilities of the all-flash XtremIO storage are fully utilized, preventing the host from becoming an I/O bottleneck. This setting is typically configured using udev rules to apply it persistently to all XtremIO LUNs.

A. Set the execution throttle to 35025: This is not a standard or recommended Linux kernel parameter for storage I/O tuning in the context of XtremIO. The value appears arbitrary and is not found in official guidelines.
B. Enable the I/O elevator: The best practice for high-performance arrays like XtremIO is to set the I/O scheduler (elevator) to noop or none, which effectively bypasses complex scheduling logic on the host.
D. Assign LUN 0 to the boot LUN: While using LUN 0 for booting is a common convention, it is not a specific performance or functional configuration guideline required to support XtremIO data volumes.

1. Dell EMC XtremIO Storage Array Host Configuration Guide (P/N 302-003-150 REV 06)

Page 100, Section: "Linux multipath configuration": This section provides an example udev rule for XtremIO devices. The rule includes the instruction ACTION=="add", SUBSYSTEM=="scsi", ATTR{vendor}=="XtremIO", RUN+="/bin/sh -c 'echo 64 > /sys/block/%k/device/queuedepth'". This directly confirms that setting the LUN queue depth to 64 is a specific guideline.

Page 100, Section: "Linux multipath configuration": The same udev rule example also includes the line ACTION=="add", SUBSYSTEM=="block", KERNEL=="sd", ATTR{queue/scheduler}="noop". This confirms that the recommended I/O elevator setting is noop, making option B incorrect.

2. Dell EMC XtremIO X2 Storage - Host Configuration Guide (August 2020)

Page 93, Section: "Linux multipath configuration": This more recent guide reiterates the recommendation. It states, "For optimal performance, Dell EMC recommends setting the device queue depth to 64 and the I/O scheduler to noop for all XtremIO volumes." This provides direct evidence for answer C and refutes answer B.