I've run Dfly for several years now, but never paused to understand
HAMMER2 (or for that matter, it's predecessor) very deeply. I've used
undo(1) a few times, but haven't dug into concepts like clustering or
even what exactly PFSes are used for. I have a feeling I'm missing out
on interesting things. So I'm finally getting around to asking a
scattershot bunch of questions. I'm using my simple one-disk setup as a
starting point. Its df -h output is below:
Filesystem Size Used Avail Capacity Mounted on
serno/5QE57G6D.s1d 193G 1054M 192G 1% /
devfs 1024B 1024B 0B 100% /dev
/dev/serno/5QE57G6D.s1a 1022M 187M 753M 20% /boot
/dev/serno/5QE57G6D.s1e@DATA 18.5G 123M 18.4G 1% /build
/build/usr.obj 18.5G 123M 18.4G 1% /usr/obj
/build/var.crash 18.5G 123M 18.4G 1% /var/crash
/build/var.cache 18.5G 123M 18.4G 1% /var/cache
/build/var.spool 18.5G 123M 18.4G 1% /var/spool
/build/var.log 18.5G 123M 18.4G 1% /var/log
/build/var.tmp 18.5G 123M 18.4G 1% /var/tmp
tmpfs 935M 0B 935M 0% /tmp
procfs 4096B 4096B 0B 100% /proc
tmpfs 935M 0B 935M 0% /var/run/shm
1. What are are the three entries that begin with "serno" and why is the
root slice not prefixed with /dev/ like the other two? What does
the nomenclature mean, specifically "5QE57G6D", "s1a" and "@DATA", for
instance).
2. Are the subdirectories under /build each their own PFS? What do those
do and why are they there? As an administrator, when would I want to
create my own PFSes? I saw someone's example of creating a set of jails
on a dedicated PFS, but I don't understand the implications of doing
that.
3. What are null mounts? It seems like that's how you mount PFSes, at
least judging by the output of the mount(1) command.
4. What are clusters, in HAMMER2? Can I use them to create a big
filesystem from storage on separate systems?
5. I think I recall hearing that the remote mirroring feature in HAMMER
is not yet supported in HAMMER2. Is that status still accurate?
6. Although I have a feeling that RAID configuration is a lower level
construct than HAMMER, what are the options? I did see that the
natacontrol(8) is able to manage RAIDs, but If I happened to get my
hands on NVMe storage, those might call for a different utility? There
is a nvmectl, but it seems like it might be for a different purpose.
Thanks,
Chuck
