How to configure a virtual disk in RHV to appear as SSD (non-rotational)?

Solution Unverified - Updated

Environment

  • Red Hat Virtualization (RHV) 4.4 SP1

Issue

  • A VM running in RHV sees its virtual disks as rotational: /sys/block/<device-name>/queue/rotational = 1
  • As the VM runs ODF, we want to present the disks as SSD.
  • ODF shows the following message: "You do not have any SSD/NVMe disks available. Data Foundation supports only SSD/NVMe disk type in internal mode".

Resolution

RHV does not support configuring if a virtual disks is rotational.

As an alternative, it is possible to configure the guest OS to override the rotational value using a udev rule: /etc/udev/rules.d/99-rotational.rules:

ACTION=="add|change", KERNEL=="sd*", SUBSYSTEM=="block", ATTR{queue/rotational}="0"

Note: configuring a rotational (HDD) disk as non-rotational (SSD) could cause issues.

In order to load the udev rule(s) without rebooting the system, execute

# /sbin/udevadm control --reload-rules
# /sbin/udevadm trigger --type=devices --action=change

Root Cause

The Linux kernel defaults to rotational for any disk that does not provide rotational info. Refer to how does the kernel determine if a SCSI disk is HDD (rotational) or SSD (non-rotational) for additional information.

Diagnostic Steps

To check if a disk is rotational (device-name could be sda/vda/nvme0n1/..., it can be checked with lsblk or fdisk -l):

# cat /sys/block/<device-name>/queue/rotational 
1
SBR
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