[Info-vax] FREESPADRIFT

[Kerry Main]

> -----Original Message-----
> From: Info-vax [mailto:info-vax-bounces at info-vax.com] On Behalf Of
> Johnny Billquist via Info-vax
> Sent: 12-Jun-16 3:18 PM
> To: info-vax at info-vax.com
> Cc: Johnny Billquist <bqt at softjar.se>
> Subject: Re: [New Info-vax] FREESPADRIFT
> 
> On 2016-06-12 21:04, Phillip Helbig (undress to reply) wrote:
> > What causes the free-space count to become wrong?  Since VMS
> obviously
> > knows about it (otherwise /REPAIR couldn't fix it), why isn't it always
> > correct?
> >
> > Is there any reason not to run ANA/DISK/REPAIR, say, once per day?
> 
> Guessing, based on RSX and ODS-1, the count is kept and updated as
> files
> are created/deleted/extended/truncated. However, there is no
> guarantee
> that nothing bad happens sometime, that is not reflected in an update in
> that count. Such as if the system crash while a file system update have
> not been flushed to disk yet. Or only partially updated.
> 
> ANALYZE, on the other hand, actually scans through all disk blocks used
> by the file headers, and then update the block used bitmap, and block
> used counts, based on this. So it is updated to become the true, correct
> count of how things actually are on disk right now.
> 
> Reasons not to run it every day? Well, that would be because you need
> to
> make sure the file system is not in use when you're running it, since
> you do not want updates done while ANALYZE is running. Also, it can be a
> rather CPU and I/O intensive operation to run ANALYZE. So it is
> inconvenient and disruptive to run it.
> 
> 	Johnny
> 

$ Help set volume /rebuild

$ Set volume user1 / rebuild ! once per day will do it (batch or whatever). 

Can be done anytime i.e. drives do not need to be dismounted.

On systems that get rebooted often (like lab systems), you can also
mount drives like this:

$ mount vol1 /norebuild/others
$ spawn set volume /rebuild

Or to force a disk block update immediately:
$ set volume /rebuild=force user1


Regards,

Kerry Main
Kerry dot main at starkgaming dot com