karpenter_node_volume_iops

Description

The karpenter_node_volume_iops parameter sets the provisioned IOPS on the root volume of Karpenter-provisioned nodes. It does not reach the EKS managed node groups, which follow node_volume_iops.

Default Value

The default value is 0, which inherits the Rack's node_volume_iops value, in the same way karpenter_node_disk inherits node_disk. With both at 0, Karpenter nodes run the AWS gp3 baseline of 3,000 IOPS.

Returning the parameter to 0 drops the field from the EC2NodeClass and puts the pools back on the inherited value, or on the gp3 baseline when node_volume_iops is also 0.

Setting the Parameter

$ convox rack params set karpenter_node_volume_iops=6000 -r rackName
Updating parameters... OK

Accepted values are 0, or 3000 to 80000. Anything else is rejected before any Terraform apply:

$ convox rack params set karpenter_node_volume_iops=1500 -r rackName
ERROR: param 'karpenter_node_volume_iops' must be 0 or between 3000 and 80000 IOPS

Changing the value rolls Karpenter nodes, paced by each pool's disruption budget, because the block device mapping is part of the EC2NodeClass drift hash.

Which Pools Receive It

The workload NodePool and the build NodePool take the value directly. Custom pools in additional_karpenter_nodepools_config inherit it unless the entry sets its own volume_iops.

Each pool is clamped at 500 IOPS per GiB of its own disk, with a floor of 3,000 when set. For the workload and build pools that disk is karpenter_node_disk, or node_disk when karpenter_node_disk is 0; for a custom pool it is that pool's disk. At the default 20 GiB the ceiling is 10,000 IOPS, and a higher request is lowered to it rather than rejected. Raising the disk size raises the ceiling with it.

Setting karpenter_config.ec2NodeClass.blockDeviceMappings replaces the generated block device list on the workload pool, which takes that pool out of this parameter. See karpenter_config.

gp3 Only

AWS takes provisioned IOPS on gp3 volumes only, so Convox renders the field on gp3 only. With karpenter_node_volume_type set to gp2, io1 or io2, neither this parameter nor a value inherited from node_volume_iops reaches the workload or build pool.

Setting it while karpenter_node_volume_type is not gp3 is rejected before apply:

$ convox rack params set karpenter_node_volume_iops=6000 -r rackName
ERROR: param 'karpenter_node_volume_iops' requires karpenter_node_volume_type=gp3 (currently io2).
  AWS takes these fields on gp3 only, so Convox does not render them on any other type.
  To raise one custom nodepool that does run gp3, set its volume_iops or volume_throughput
  in additional_karpenter_nodepools_config instead

Moving karpenter_node_volume_type off gp3 while a value is already stored is accepted, and prints a line to stderr:

WARNING: karpenter_node_volume_iops no longer applies to the Karpenter workload and build pools now that karpenter_node_volume_type is io2. Custom nodepools that set volume_type gp3 still receive it.

A custom pool is judged on its own volume_type, which defaults to gp3, so a pool that sets nothing keeps receiving provisioned IOPS on a Rack set to another type.

Additional Information

This parameter is available on AWS Racks only and requires Rack version 3.25.7 or later. Setting it also requires a convox CLI at 3.25.7 or newer; an older CLI rejects the name as an unknown parameter, so run sudo convox update first.

• The parameter is not clearable. convox rack params set karpenter_node_volume_iops= is rejected with param 'karpenter_node_volume_iops' requires an explicit value (omit to keep current). Pass 0 rather than an empty value.
• Enabling Karpenter: on a Rack with high_availability set to false, this parameter cannot be set in the same call as karpenter_enabled=true. Set it first, wait for the update to finish, then enable Karpenter.
• Parameter groups: karpenter and storage. convox rack params -g storage -r rackName lists it next to the other volume settings.
• convox rack params lists stored values only, so karpenter_node_volume_iops does not appear in that output until you set it.

See Also

• Karpenter for the full Karpenter configuration reference
• karpenter_node_volume_throughput for the throughput on the same volume, which is capped at a quarter of these IOPS
• karpenter_node_volume_type for the volume type that gates this parameter
• karpenter_node_disk for the volume size that sets the 500-per-GiB ceiling
• node_volume_iops for the Rack-wide value this parameter inherits at 0