From: Steve Losen [mailto:scl@sasha.acc.virginia.edu]
We want to upgrade a FAS960c cluster from 7.0.0.1 to 7.0.1R1. The cluster is only doing FC SAN, providing LUNs for our central email servers, which are Suns running Solaris 8 and Veritas volume manger and filesystem. Veritas is configured to to multi-pathing.
We do not want to schedule downtime for the email servers whenever we upgrade the filers. I have been reading about the "non disruptive" upgrade procedure where you install the new system files, download, and instead of reboot, you "cf takeover" one filer and "cf giveback", then do the same with the other filer.
Is this really significantly less disruptive than doing a normal upgrade where you "cf disable" and then just reboot both filers?
Hi Steve,
The non-disruptive upgrade (NDU) process is the same level of disruptiveness as a reboot (e.g. no disruption for NFS; connection lost for CIFS). The difference is that the length of time the filer isn't servicing the clients is shorter in the NDU case. The takeover time, while dependent on the load of the filers, is faster than a reboot which requires the filer to do POST, load the kernel, scan the Pci bus, init the adapters, init all the processes, etc.
When you "cf takeover" the current SAN data path that the Sun boxes are using to access some LUNs becomes unavailable, so they must switch to an alternate data path through the surviving filer. How long does this take and how disruptive is it? Then when you "cf giveback", the Sun boxes need to switch back to the original data path. If you simply reboot both filers, then all of the LUNs are unavailable during the reboot and come back after a minute or two.
I've cc'd our FCP person for his answer to this but again the service "pause" is shorter for takeover/giveback then a reboot.
Is it really less disruptive and "safer" to use the takeover/giveback procedure in our situation?
NDU is a tested, documented procedure.
I am also concerned about the disk firmware upgrade that may happen as part of an ONTAP upgrade. Is it better to upgrade the disk FW before upgrading ONTAP, to make the ONTAP upgrade as fast as possible?
Yes, in fact the current recommendation is that you don't use NDU if you need a disk f/w upgrade and you have raid-4 aggregates. It is ok to use NDU if you use raid-dp or mirrored raid-4 aggregates.
-Steve Watanabe NetApp Cluster Group
Steve Losen scl@virginia.edu phone: 434-924-0640
University of Virginia ITC Unix Support