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From: Ensel Sharon <user@dhp.com>
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Subject: tuning to run large (1000+) numbers of null_mounts
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I am running over 2000 null mounts on a FreeBSD 6.0-RELEASE system.  I am
well aware of the status of the null_mount code, as advertised in the
mount_nullfs man page:

     THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T
WORK)
     AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM.  USE AT YOUR
OWN
     RISK.  BEWARE OF DOG.  SLIPPERY WHEN WET.

So, based on this, all of my null_mounts are actually mounted read-only.

I am noticing both system instability and data corruption issues on disk
following crashes.  Both of these seem to be related to the null
mounts.  I have two very quick questions:

1. Is my theory that using only read-only null mounts is a good way to
avoid data corruption a sound one ?  Or can even a read-only null mount do
bad things to underlying data ?

2. What system tunes / alterations would be appropriate for a system
running several thousand (although, always less than 5000) null mounted
filesystems ?

Please relay _any and all_ comments, suggestions, war stories,
rumors.  They are very appreciated.