[Info-vax] BACKUP/INIT

[Jan-Erik Soderholm]

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:

      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.