2023-06-29
The persistence of 'san' names in our environment
We have a bunch of Linux fileservers, which use ZFS pools on ordinary SATA SSDs and export the filesystems from those pools over NFS. To make managing this environment easier, we have a suite of local programs (including our own ZFS spares system). All of these tools have names that start with 'san' (for example 'sanpool' and 'sanspares'). All of the hostnames of the fileservers also start with 'san' (they're mostly but not entirely named after cities, so we have 'santafe' but also 'sanandreas', which is of course the test fileserver). All of this is despite there being no SAN (Storage Area Network) in sight.
Of course there is history here. The first layer of history is that our current set of fileservers only dates to 2018, and they're the third generation of ZFS fileservers we've had. Before 2018 we had first a Solaris generation and then an OmniOS generation, both using the same basic approach of Solaris/OmniOS frontends using iSCSI to talk to Linux based backends that had the actual disks. Although back in the days we thought of our first and second generation ZFS fileservers as having a SAN (or two), it was sort of a discount SAN, since it was a couple of manually managed subnets, two switches (one for each subnet), and machines connected to both that talked iSCSI with each other. Although we used 'san' names even in the first generation of ZFS fileservers (and our local management programs are that old) and thought of this as a SAN, the SAN-ness goes back even further, to a true SAN.
Before our first generation of ZFS fileservers, we had a NFS server environment that used Solaris 8 and DiskSuite (later 'Solaris Volume Manager'). These machines used a genuine Fibre Channel SAN to 'hardware' RAID controllers, complete standard SAN things like failover. Our later iSCSI environment was built in deliberate imitation of this setup, even if we didn't manage to use things like failover. This completely different set of fileservers also had 'san' hostnames and had commands and scripts with 'san' in their names (and a local configuration file called 'sanconfig', a name we reused for the ZFS fileserver generation).
So, depending on how you think of it, we haven't had a SAN since either 2018 (when the disks became local to the fileservers) or 2008 (when we moved from the FC based environment to the ZFS and iSCSI one). Despite that, the san names have lived on, and they'll probably still be in use for as long as we have a ZFS based fileserver environment. Sure, we could rename the programs and change the hostnames we give fileservers, but we're used to the current names, even if they're not quite accurate any more.