fault toleratant shell scripts

[Bill Vermillion]

On Tue, Mar 16, 2004 at 12:36:31AM -0500, Jay R. Ashworth thus spoke:
> On Tue, Mar 16, 2004 at 12:30:52AM -0500, Ward Griffiths wrote:
> > On Monday 15 March 2004 01:36 pm, Bill Vermillion wrote:
> > > And you didn't remove everything in the system.  Since could could
> > > not remove the directory you were in, the only thing it left
> > > was the /usr/spool/lpd/<whatever> loop as it tried to descend
> > > furhter and further.  It was just like a hoop snake in that
> > > respect.  [If you reember the stories of the hoop snake from your
> > > youth]

> > /bin/rm (and /bin itself, naturally) would also remain.
> > Tested that once on a store demo I was cleaning up for a
> > fresh OS install for a customer delivery -- did an rm -f *
> > from / then mounted and looked at the HD from a boot floppy
> > just for grins. Then I formatted it.

> Wimp. 

> *I* did it on a live system.

> 16B, Xenix 3, Real World.

> # cd /error/in/path/name
> cd: path not found
> # rm -rf .
> rm: you friggin' idiot
> ...

> Got it stopped after a couple *minutes*. It ate a *lot* of
> stuff. But, amazingly, not so much that a) the users stopped
> being able to work or b) we were unable to back the data up and
> reload from the prior night and restore.

In today's world you only have a couple of seconds.
With the softupdates in FreeBSD I can perform an rm -r on a OS
source tree - about 350MB - and have the prompt back in about 5-10
seconds.   It takes from 1-2 minutes for all the space to be
reclaimed as it performs that task in the background.  The first
thing it does is update the meta-data, so that even a power-off
shortly after you start the process returns a coherent file system,
and then any unremoved blocks will get fixed on reboot.

In the 5.x series even the reboot clean up is done in the
background.  I'd not like to wait waiting for a NN TB file system
to clean itself.

And Apple - not known for cheap products - now sells a 3.5 Terabyte
drive array for a list price of $10,999.

You can get 49 Terabytes of storage in a standard 5 foot [42RU]
rack.  And I remember the first big drives I saw.  About the size
of a large Kenmore washing machine and they had 70MB.  Westinghouse
had a room of them that looked more like the appliance section of
the local Sears store.

> I *was* on site until something like 0130...

One I did like that I left at 130AM, and came back at 630AM as I
figured the slow tape restore would be done about then.

Much to my dismay, the tape drive physically failed, so the next
day it was build up from ground zero, and then move the files
from another system where I could at least read the tape and then
ftp them over.

Days like that you think "Why did I give up hardware for this
software crap" :-0

Bill

-- 
Bill Vermillion - bv @ wjv . com