zfs home directories best practice

[Graham Allan]

We're building a new NFS home directory server on FreeBSD with ZFS. The 
Solaris ZFS Best Practices docs say to create a separate filesystem for 
each user home directory. My instinct is to ask "Are you serious???". My 
gut feeling isn't entirely logical but the idea of getting 1000+ lines 
of output from a simple "df" just feels wrong...

Can anyone comment about how well this approach actually works, 
specifically on FreeBSD? (we're running 9.1) Obviously it has some nice 
features, such as quota controls, snapshots directly available to users 
within their home, etc, but it leaves me concerned. I chatted with some 
neighbors who have a larger, Solaris-based shop, and they said that with 
10,000 user home filesystems, their server could take an hour to boot 
(at least using the default startup scripts). They reverted to having 
one big shared filesystem for all, but would like to revisit the 
per-user approach with fewer users per server.

Ours wouldn't be so large, but we could easily have around 1000 user 
filesystems. I haven't tested yet what effect that would have on boot 
time, though hope to test it over the next week. Perhaps it implies 
other resource usage besides the boot time issue (is there any limit to 
number of filesystems mounted or NFS-exported?). I wonder if anyone here 
has built a system along these lines and has experiences to share.

Thanks for any comments,

Graham
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Graham Allan
School of Physics and Astronomy - University of Minnesota
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