Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!hp-pcd!hpfcso!hpfcdc!brucet
From: brucet@hpfcdc.HP.COM (Bruce Thompson (greeley temp))
Newsgroups: comp.sys.hp
Subject: Re: Optical Library Management Schemes
Message-ID: <5570631@hpfcdc.HP.COM>
Date: 13 May 91 22:45:36 GMT
References: <1991Apr30.191403.6571@batcomputer.tn.cornell.edu>
Organization: HP Fort Collins, Co.
Lines: 36

>>What this means to you is that all the cartridges can be mounted rw
>>at boot time at the desired mount points.  Users do not have to
>>mount a cartridge, access it, then unmount it.  You do not have
>>to make /etc/mount suid!

  >Does this mean that when a user types bdf the autochanger makes
  >a lot of noise and returns in about a minute?  What happens when
  >I try and "sync" the machine before I shut it down?  It seems that
  >the mechanical delays in the autochanger would negate sync's
  >efficiency.


The bdf (and df) command has been modified in 8.0 to not cause all mounted
file systems in the autochanger to be inserted into a drive.
It grabs all the information it needs from kernel memory, therefore
no cartridge swaps are performed.  

The function of "sync" is to schedule up dirty buffers to be
written out to the disk.  What happens with the autochanger is
that before a cartridge is removed from the drive, all the dirty
buffers are flushed out.  Thus when "sync" runs , it won't find 
any of those old dirty buffers so no extra cartridge swaps
will be performed.   Any new dirty buffers created since the last time the 
cartridge was inserted will be written out the next time the 
cartridge is inserted.

As for shutting down the system, when "umount -a" runs it will
unmount all mounted file systems.  Since cartridges which are
"mounted" but stored in slots have all the system buffers flushed
and the superblock marked clean, only the kernel data structures
are cleared.  Cartridges currently in drives will be ejected
an returned to their slots.  Thus the time to  shutdown a system with
an entire autochanger filled with cartridges mounted read-write
is only increased by a few seconds. 

Bruce Thompson