Home > Storage > PowerScale (Isilon) > Product Documentation > Management and Migration > Dell PowerScale: Non-Disruptive Upgrade Best Practices > Drain-based upgrade
During an upgrade workflow, nodes will get a reboot or the protocol service must be stopped temporarily. This leads to a quick disruption to the clients connected to the rebooting node. This feature provides a mechanism by which nodes are prevented from rebooting or restarting protocol services until all SMB clients have disconnected from the node. A single SMB client that does not disconnect can cause the upgrade to be delayed indefinitely and so the user is provided with options to reboot the node despite persisting clients.
The drain-based upgrade supports the following scenarios and is available for WebUI, CLI, and PAPI.
The drain-based upgrade is built upon the parallel upgrade workflow which is introduced in OneFS 8.2.2.0 which offers parallel node upgrade and reboot activity across node neighborhoods. It upgrades at most one node per neighborhood at any time. By doing that, it can reduce upgrade duration and ensure that the end- user can continue to have access to their data. The more node neighborhoods within a cluster the more parallel activity can occur.
Figure 3 shows an example of how it works. In this case, we assume there are two neighborhoods in a given 6 node PowerScale cluster. Node 1 to node 3 belongs to neighborhood 1 and Node 4 to node 6 belongs to neighborhood 2. You can use the following command to identify the correlation between your PowerScale nodes and neighborhoods (failure domains):
# sysctl efs.lin.lock.initiator.coordinator_weights
Once the drain-based upgrade is started, at most one node from each neighborhood will get the reservation which allows the nodes to upgrade simultaneously and OneFS will not reboot these nodes until the number of SMB clients is “0”. In this example, Node 3 and Node 4 get the reservation for upgrading simultaneously.
However, there is 1 SMB connection for Node 3 and two SMB connections for Node 4. They cannot reboot until the SMB connections get to “0”. At this stage, there are three options:
# isi upgrade start --parallel --skip-optional --install-image-path=/ifs
/data/<installation-file-name> --drain-timeout=60m --alert-timeout=45m