[Info-vax] BACKUP/INIT

[Phillip Helbig---undress to reply]

In article <ijlsmf$62ä1 at news.albasani.net>, Jan-Erik Soderholm
<jan-erik.soderholm at telia.com> writes: 

> jbriggs444 wrote 2011-02-18 14:20:
> > On Feb 18, 4:51 am, hel... at astro.multiCLOTHESvax.de (Phillip Helbig---
> > undress to reply) wrote:
> >> I just did INIT/SYS several times on a 1-GB disk (RZ26L).  I kept
> >> getting a cluster size of 16, even though I didn't specify this.  This
> >> is with VMS 7.3-2.
> >>
> >> In the old days, I never specified cluster size.  With 1-GB disks, I
> >> always got 3.  According to HELP BACK/INIT, I should get this since it
> >> is larger than what is otherwise used as the default.  Why in the world
> >> should I get 16?  It's not even a default in any situation.  I just had
> >> INIT/SYS/HEADERS=50000, nothing else.
> >
> > In the old days my recollection is that there was a hard limit on the
> > size of bitmap.sys and, as a result, the number of allocation clusters
> > on the volume had a hard cap.  Make the volume big enough and
> > the default cluster size of 3 is inadequate to allow bitmap.sys to
> > cover
> > the whole volume.
> >
> > INITIALIZE was aware of this and would bump up the cluster factor
> > for large volumes.
> 
>  From HELP /INIT :
> 
>       For Files-11 On-Disk Structure Level 5 (ODS-5) disks, the default
>       cluster size is 16. In this case the minimum value allowed by the
>       following equation is applied:

I'm on 7.3-2; HELP says:

     For Files-11 On-Disk Structure Level 5 (ODS-5) disks, the default
     cluster size is 3. In this case the minimum value allowed by the
     following equation is applied:

But that is neither here nor there since it is ODS-2.

>       For Files-11 On-Disk Structure Level 2 (ODS-2) disks, the default
>       cluster size depends on the disk capacity; disks with less than
>       50,000 have a default of 1. Disks that are larger than 50,000
>       have a default of either 16 or the result of the following
>       formula,  whichever is greater:
> 
>       (disk size in number of blocks)/(255 * 4096)
> 
> For 1 GB that gives 16.

Volume size in blocks for 1 GB is 2050860.  255 * 4096 = 1044480.  That 
gives 1.96, which is smaller than 3, so I get 3.

     For Files-11 On-Disk Structure Level 2 (ODS-2) disks, the default
     cluster size depends on the disk capacity; disks with less
     than 50,000 have a default of 1. Disks that are larger than
     50,000 have a default of either 3 or the result of the following
     formula, whichever is greater:

     (disk size in number of blocks)/(255 * 4096)

     Any fractional values must be rounded up to the nearest integer.

Again, 7.3-2 HELP, but that is what I am on.

Apparently, some patch changed the default and HELP wasn't updated.  (3 
was definitely the default for a 1-GB disk some years ago, as my old 
disks indicate.)  Whatever happened to quality control?

Interestingly, I had decided on 16 as my personal default for most of my
disks.