File identification problem.

[Robert Brooks_1]

Any 3rd-party caching products in use?

Do the disks have multiple paths?

-- Rob

[John McL]

Murali, the disk defragger that I had problems with was many years ago. It was a third party product - might have been Raxco, I'm having trouble recalling it.

I'm not even sure that it was strictly a defragger problem. It might have been errors on the disk that were made worse with the files being defragged (and obviously new disk blocks written).

We ended up with ANALYSE/DISK reporting the very nasty "multiply allocated blocks" (as in "multiple-ly") and I had to examine about 150 files to work out which of two files the blocks actually belonged to.

[John Gillings]

>defragger that I had problems with was many
>years ago

yes MANY years, like the mid 1980's! The last one I caught red handed was called "Rabbit7" in about 1990.

For the first decade or so of OpenVMS history, the digital party line was that defragmentation was unnecessary, and the company did not have a defrag product (other than image backup & restore). In one of the rare cases of OpenVMS management responding to market forces, they finally realised that regardless of technical pontificating about the features of the file system, people WANTED to defrag files, if only for the warm fuzzy feeling of everything neat and tidy.

OpenVMS introduced the "MoveFile" primitive function at the XQP level which gave a supported and reliable mechanism to correctly synchronise defragmentation as an atomic and crash proof operation. I think it was around V6, early 1990s.

As well as the digital product (known by various names, DFG, DFO, PFO...), the 3rd party products changed from rather dodgy hacks to using the proper interface, and most (though perhaps not all) defragger related disk corruption vanished overnight. Support centres no longer saw file systems with "muddy rabbit tracks" all over them.

[Robert Brooks_1]

OpenVMS introduced the "MoveFile" primitive function at the XQP level which gave a supported and reliable mechanism to correctly synchronise defragmentation as an atomic and crash proof operation. I think it was around V6, early 1990s.

---
It was definitely before V6; V5.5 or V5.5-2, I think, 1992ish.


-- Rob

[P Muralidhar Kini]

John MCL, John Gillings,
Thanks for the information.
Good to know the history about the XQP's MOVEFILE primitive.

>> might have been Raxco, I'm having trouble recalling it.
May be you are referring to PD (Perfect Disk)

>> We ended up with ANALYSE/DISK reporting the very nasty "multiply
>> allocated blocks" (as in "multiple-ly") and I had to examine about 150 files
>> to work out which of two files the blocks actually belonged to.
Ahh. Must have been a painful experience.

It would have been interesting to know if Dave had any defraggers installed in
his system. If Yes then is the Disk/File enabled for defragmentation.

Regards,
Murali