[Info-vax] FREESPADRIFT

[Paul Sture]

On 2016-06-16, lawrencedo99 at gmail.com <lawrencedo99 at gmail.com> wrote:
> On Friday, June 17, 2016 at 6:24:46 AM UTC+12, Michael Moroney wrote:
>
>> Don't forget that Spiralog was newer than ODS-5/ODS-2.  And Spiralog was
>> to be a different file system for VMS (not a mod to ODS-5) but was 
>> cancelled.
>
> Linux was able to add journalling to an existing filesystem (turning
> ext2 into ext3). VMS never did the same?

A mentioned by another poster, work was started on a new filesystem.

We're back to where you spend the available resources - retrofitting
a new feature to an existing system or implementing a replacement?

The existing VMS filesystem doesn't cache writes as much as other file
systems, and on-disk pointers are built in such a way that a power loss
doesn't result in the damage you see on other file systems.

I'd put it that the current VMS filesystem didn't need journalling as
urgently as other filesystems.

And yes, the relative certainty that when you write something to disk
it the current VMS world, it does actually hit the disk, has been a
limiting factor in performance.

-- 
There are two hard things in computer science, and they are cache invalidation,
naming, and off-by-one errors.