--On Friday, May 20, 2011 02:28:18 PM -0700 John R Pierce <pierce at hogranch.com> wrote: [snip] > One question I have is: how well will this scale with several strings of > 100 SAS drives on the same HA pair of servers? > > Can SAS storage instead be fenced at the SES/expander level rather than > having to use reservations with each separate drive? It's been a few years since I've used SCSI reservations as a fencing method (as in about the time that wide SCSI was taking over from narrow SCSI, and while it fenced nicely, it sometimes caused bus errors when you detached the dead node from the bus). However if you are using a set of disks as a logical unit from the cluster's perspective (like having set of disks acting as a RAID device), then IIRC it is sufficient to use a reservation on a single disk as your fence for the entire disk set (rather than using a reservation on every single disk). Of course, of your storage cabinet has a few different disk sets in it, you'd need additional reservations (one per set). But, as I said, it's been a few years so I'd investigate it more rather than depending on *just* the above comment. In recent years I've tended to use various mechanisms to kill power to the node as my preferred fencing method. The linux-ha and pacemaker lists may be a better source of current information. Devin