tuning to run large (1000+) numbers of null_mounts

[Ensel Sharon]

On Wed, 18 Jan 2006, Kris Kennaway wrote:

> > hmmm...the cut and paste of that loud warning was from a 6.0-RELEASE man
> > page ... if I need to be CURRENT to get the updated man page, do I also
> > need to be CURRENT to get the safe null_mount code itself ?
> > 
> > Or is 6.0-RELEASE safe ? (re: null_mount)
> > 
> > Thanks a lot.
> 
> 6.0-RELEASE is also safe.  I only just removed the warning the other
> day, but I'll also be merging it to 6.0-STABLE.


Ok, that is good to know.

However, I continue to see instability on this system with the 2000+
null_mounts.  Are there any system tunables / sysctls / kernel
configurations that I should be studying or experimenting with that are
relevant to this ?

Perhaps looking more broadly, are there any tunables related to large
numbers of mounted filesystems _period_, not just null mounts ?

For what it is worth, the system also has several mdconfig'd and mounted
snapshots (more than 5, less than 10).  Further, all of the null mounts
mount space from within a mounted snapshot into normal filesystem space.  
With all the snapshots mounted and all the null mounts mounted, I find
that commencing an rsync from the filesystem that all these exist on locks
up the machine.  I can still ping it, but it refuses all connections.  It
requires a power cycle.

Comments ?