[Info-vax] VMS and the (lack of the) TRIM facility.

[JF Mezei]

On 15-06-20 13:27, David Froble wrote:
> Ok, there are at least 2 scenarios.  Direct attach and SAN.  For SAN, 
> such problems should be handled entirely within the SAN. 

the SAN sees from VMS requests to rewrite a few blocks.  So the SAN
would need to spot a rewrite to INDEXF.SYS, know the exact structure of
the file AND detect exactly what changes are being made in the rewrite
so that it can look at the old version to see which blocks were occupied
by the deleted file so that it can then issue TRIM commands to the SSDs
that holds those blocks.

Unless the SAN runs MSCP and gets high level MSCP commands and manages
the ODS-x disks itself, it doesn't have a realistic chance of knowing
that a block being updated is really due to a file being deleted as
opposed to someone updating their dietary preferences in their flight
reservation record.