[Info-vax] From ODS-2 to ODS-5

[geze...@rlgsc.com]

On Thursday, August 20, 2020 at 9:23:36 PM UTC-4, Steven Schweda wrote:
> > [...] I'd rather be on the safe side and have a backup. 
> 
> If you want a backup, then make a backup. Then SET VOL. 
> Why waste the time on what should be a pointless restore 
> operation? 
> 
> If I wanted to test SET VOL, then I'd play with some 
> unimportant disk. Virtual, probably. 
> 
> It's been a _long_ time since I switched to ODS5 system 
> disks for non-VAX systems (and SET PROC/PARS=EXTE, too), but 
> I believe that I did at least one using SET VOL. As I 
> recall, it took approximately no time.
> > I was more concerned about the various sizes. Will they be 
> > the same or will SET VOL inherit old sizes from 2 while INIT 
> > will use new sizes for 5?
> _Which_ "the various sizes"? Why would the size(s) of an 
> existing file change? If the cluster size changes, then I 
> might expect a _new_ file to differ from a similar old file. 
> I don't see /CLUSTER_SIZE among the options on SET VOLUME. 
> 
> If you _want_ a newer/better/smaller cluster size, then 
> INIT (and BACKUP) might be a better choice than SET VOL. 
> 
> You might be thinking too hard about this.
Arne,

Unless the disk is a scratch disk, IMHO, a pre-conversion backup cannot hurt. At worst, it is superfluos. I would not expect a problem with the SET VOLUME, but the usual precautions about important data apply.

I concur with Rob. Worry about the cluster factor is probably misplaced. The cluster factor can be reduced, but it cannot be increased. Try some cases. Ignoring the bitmap size issue, all structures can be reduced to a cluster of 1. Otherwise, the cluster size can be reduced to a prime factor of the extant cluster factor, e.g. a cluster factor of 5 can be reduced to 1; 10 can be reduced to 2 or 5; 30 can be reduced to 5, 6, 10, or 15.

- Bob Gezelter, http://www.rlgsc.com