FreeBSD & no single point of failure file service

[J David]

Hello,

I would like to build a file server with no single point of failure, and I
would like to use FreeBSD and ZFS to do it.

The hardware configuration we're looking at would be two servers with 4x
SAS connectors and two SAS JBOD shelves.  Both servers would have dual
connections to each shelf.

The disks would be configured in mirrored pairs, with one disk from each
pair in each shelf.  One pair for ZIL, one or two pairs for L2ARC, and the
rest for ZFS data.

We would be shooting for an active/standby configuration where the standby
system is booted up but doesn't touch the bus unless/until it detects CARP
failover from the master via devd, then it does a zpool import.  (Even so
all TCP sessions for NFS and iSCSI will get reset, which seems unavoidable
but recoverable.)

This will be really expensive to test, so I would be very interested if
anyone has feedback on how FreeBSD will handle this type of shared-SAS
hardware configuration.

Thanks for any advice!