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

[Michael Moroney]

Dirk Munk <munk at home.nl> writes:

>> (other erase patterns can be defined and erased blocks can be written
>> multiple times for data security reasons, but that's not applicable here)
>>

>I don't understand this. The "erase block" command is a function of the 
>drive, do you mean to say that with a HDD you can tell the drive to 
>erase a block, and also specify which pattern to use?

The IO function IO$_DSE is intended to erase data by overwriting it with
a pattern (or multiple patterns for use by three letter agencies).  It
special cases a pattern of all zeroes, or no pattern specified, to do the
drive level erase rather than writing with a pattern of zeroes, for drives
that suppport doing so.  These days, that's the primary use of the 
function.  It's much faster to tell a drive to erase a range of blocks 
than it is to write them with zeroes.