The csi-hpe module: FAQ

What are the requirements for the csi-hpe module?

The csi-hpe module requires:

• Presence of a deployed and configured HPE SAN.
• Unique iqn in /etc/iscsi/initiatorname.iscsi on each of Kubernetes Nodes
• The snapshot-controller module must be enabled in the cluster (required for volume snapshot functionality).

How to check module health?

To do this, you need to check the status of the pods in the d8-csi-hpe namespace. All pods should be in the Running or Completed state and should be running on all nodes.

kubectl -n d8-csi-hpe get pod -owide -w

How much of a volume is reserved for the superuser?

Nothing, by default: the module tells the driver to format ext4 with -m0, so the whole volume is available to the workload.

Where the classic 5% ext4 reserve is wanted — for example to keep a filesystem writable for a privileged process after a workload has filled it — annotate the HPEStorageClass with the percentage to reserve:

d8 k annotate hpestorageclass <name> storage.deckhouse.io/ext4-reserved-percent=5

The value is a whole number of percent between 0 and 50; an invalid one leaves the HPEStorageClass with Ready=False and the reason in its status, instead of breaking volume creation later.

The reserve applies only to volumes created after the annotation was set — filesystems that already exist keep the reserve they were created with. A class with fsType: xfs is unaffected: XFS keeps no blocks for the superuser.

Changing the annotation makes the controller recreate the StorageClass, because parameters of an existing StorageClass are immutable in Kubernetes. Existing volumes and PVCs are not affected.

What happens if a node’s repositories cannot provide open-iscsi and multipath-tools?

The module installs them itself, from an image of its own.

On every node it serves, the NodeGroupConfiguration first asks the node’s package manager for open-iscsi and multipath-tools. That stays the preferred path: a host’s own client and daemon are what the rest of that host is built around, and nothing about them is the module’s business while they are there.

When the install fails — a closed environment with no route to the repositories, or a distribution that does not ship the packages — the module falls back to its own package image, iscsi-tools. bashible pulls it from the module’s registry, unpacks it on the node and runs its install script. The payload lands under /var/lib/deckhouse/sds/csi-hpe, every binary is started through its own dynamic loader with its own library path, and two units come up for the daemons:

systemctl is-active d8-csi-hpe-iscsid.service d8-csi-hpe-multipathd.service

Two things the install script arranges that are worth knowing about, because both are invisible until something does not mount.

The driver reaches the host’s iscsiadm through the container’s /bin/iscsiadm, which is the in-tree host-iscsiadm binary: it chroots into /host and looks the client up there, against a PATH of its own. The script leaves a wrapper at /usr/local/sbin/iscsiadm, which that PATH searches ahead of the distribution’s directories, and the wrapper defers to a distribution iscsiadm the moment one appears.

And multipathd from the package reads its configuration under the prefix it was built with, not under /etc. The script links multipath.conf and multipath from that prefix onto the node’s own. That matters more here than anywhere: the driver locates a staged LUN only through its device-mapper map, so the find_multipaths no this module writes into /etc/multipath/conf.d is the difference between a working attach and device not found with serial <wwn>.

The two paths never mix. A host that already has iscsiadm of its own keeps everything of its own, and the install script does nothing there: the client and the daemon must always come from the same source, because iscsiadm of one version does not speak to iscsid of another.

To tell which path a node took, look at what is running on it:

# the distribution's stack
systemctl is-active iscsid multipathd
# the module's own
ls /var/lib/deckhouse/sds/csi-hpe/bin
multipathd show config | grep find_multipaths

Two things the fallback deliberately does not change. It never merges anything into the host’s /lib64 or /usr/lib — the payload is self-contained. And it does not touch /etc/iscsi/initiatorname.iscsi when the node already has one: the IQN is the node’s identity on the array, registered there in a host object, and a node that comes back under a different name is a node the array has never heard of.

sg3-utils is asked of the distribution but is not in the fallback, and nothing is lost by that: the driver’s only call into it was rescan-scsi-bus.sh, which this module’s patches replaced with direct sysfs writes.