Re: blkdiscard vs hdparm for erasing a SSD?

[Peter Wu <peter-VTkQYDcBqhK7DlmcbJSQ7g@public.gmane.org>]

On Wednesday 15 October 2014 15:21:18 Tim Small wrote:
> On 15/10/14 14:12, Peter Wu wrote:
> > [ blkdiscard vs hdparm --security-erase] How does this compare. The goal is
> > to erase the contents of an previously used SSD to improve performance.
> >
> 
> When you use blkdiscard, the SSD (assuming a SATA SSD) will receive an
> ATA TRIM command, whereas hdparm --security-erase will issue an ATA
> SECURITY ERASE UNIT command.
> 
> What the drive then actually does is dependant on the implementation
> details of that particular SSD's firmware.
> 
> In general, I would expect the performance gain from TRIMing the entire
> drive to be either the same-as, or possibly less-than the gain from
> SECURITY ERASE.  For a sane firmware implementation I'd expect them to
> have the same effect on performance.  Firmware implementations are not
> always sane.

The names suggest that TRIM is for marking sectors for garbage collection while
SECURITY ERASE tries a bit harder. From the runtime performance point of view, I
would expect that S.E. is at least as fast as TRIM as no more garbage needs to
be collected at a later point. From a durability PoV, not so sure, it could be
that S.E. overwrites all blocks (or not).

Anyway, I have not read into the details and unless the standards (and
manufacturers) can guarantee certain behavior, it will likely vary between
device models.

Thank you for your reply!
-- 
Kind regards,
Peter
https://lekensteyn.nl

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