Brocade warm reboot

[Alexey1]

Hi there

when we do a FabricOS upgarde for a "pizza box" switch, at some stage Fabric OS does a warm reboot to boot a new version of software.

At the same time the traffic is continued to being served. I wonder how exactly is it implemented. Could not find any documentation.

Have you seen any detialed explanations, some tech articles?

Regards,

Alexey

[cedric_renauld]

In case of SAN Brocade, normaly, you may have 2 Fabric, a minimm of tow switches, 1 for Fabric 1 and another for Fabric 2

This multiple fabric give to your hosts a multipath access to your LUN storage

When you update a SAN fabric, the IO are frozen, but you can do that fabric after fabric, that give to your hosts always one path to the storage

[Alexey1]

Well, it's not about having two fabrics. According to the FOS Upgrade Guide, the warm reboot is nondisruptive.  Only Generic Services are affected, so the switch will not be able to register a new device for example.

However, switch continues to transfer frames. So IO is not frozen.

Im curious how this is achieved.

All Brocade systems maintain two partitions (a primary and a secondary) of a nonvolatile storage to store the firmware.
The firmware download process first copies the replacement files (containing an updated kernel) into the secondary
partition. Then, the process swaps the partitions so that the secondary partition becomes the primary. It then performs
a nondisruptive HA reboot of the system. For directors, the standby is rebooted; this does not affect the system traffic. The
system attempts to restore the previous machine state after the reboot is completed for fixed-port platforms, also called a
warm reboot. When the system boots, it boots using the revised Fabric OS firmware in the primary partition. The firmware
download process then copies the updated files from the primary partition to the secondary partition.
NOTE
Most firmware upgrades and downgrades are not disruptive to device operations; however, always refer to the
latest Fabric OS release notes for updates on upgrading and downgrading.

NOTE
During the (HA) reboot on fixed-port switches, exchanges involving Fibre Channel Generic Services may
experience a delay. Fixed-port switches must retry the operations in this case.