[Info-vax] Reclaim disk space for a 3PAR Storage Box

[David Jones]

On Monday, August 30, 2021 at 8:19:54 AM UTC-4, Simon Clubley wrote:
> On 2021-08-30, Volker Halle <volker... at hotmail.com> wrote: 
> >> My problem is that for big disks (800GB) with a low used space, we create thousands and thousands of files and the DELETE/ERASE takes days. 
> > 
> > Bruno, 
> > 
> > on those big disks, is DELETE/ERASE the problem or the fact, that you have to delete 'thousands and thousands' of (small) file in ONE directory ? How big is the .DIR file after you've created those temporary 10 MB files ? Would it help, to DELETE/ERASE those files in reverse order, i.e. highest version number first ? This would reduce the shuffling of entries in the directory. 
> >
> If he has a range of filenames, version numbers will not be the only issue 
> here, but also the ordering of the filenames in the directory file. 
> 
> He needs to delete files in reverse name order _and_ for a given filename 
> needs to delete those files in reverse version number order as you say above. 
>

A directory entry has a filename and a list of version+file-id values with the highest version first (8 bytes per file version).
Unless you have enough versions of a file to force multiple directory records for it (directory records can't span blocks),
it doesn't make much difference the order they are deleted in. If you do have multiple records, you want to delete them
is ascending version order (which is opposite of how they are returned by SYS$SEARCH()).

> Hard to believe that this is still a problem on VMS in 2021. 
>

It can still be a problem on Unix, depending upon the file system you are using.