Ceph iSCSI Interface

In this article we set up iSCSI interface on a Ceph cluster. According to the official documentation, the iSCSI gateway is in maintenance as of November 2022. New features will not be provided.

Requirements

For iSCSI gateways, we will use hosts managed by cephadm. These hosts will be listed with this command.

 sudo ceph orch host ls

We first pick nodes for iSCSI gateway nodes. Here, let us assume that three OSD nodes are chosen: ceph-osd01, ceph-osd02, and ceph-osd03. A dns name for each node needs to be available on all the three nodes.

Recommanded Configuration Changes

To avoid initiator timeouts, three configuration parameters are suggested to be updated: osd heartbeat grace/interval and client watch timeout. The suggested values are 20, 5 and 15, respectively.

The following commands will query values of these parameters.

sudo ceph tell osd.* config get osd_heartbeat_grace
sudo ceph tell osd.* config get osd_heartbeat_interval
sudo ceph tell osd.* config get osd_client_watch_timeout

If they need to be changed, use these commands.

sudo ceph config set osd osd_heartbeat_grace 20
sudo ceph config set osd osd_heartbeat_interval 5
sudo ceph config set osd osd_client_watch_timeout 15

Prepare a RBD pool for iSCSI disks