Re: Shutdown - 25 Years Later

The Natural Philosopher <tnp@invalid.invalid> writes:

On 22/04/2025 09:35, Carlos E.R. wrote:

On 2025-04-21 02:29, Lawrence D'Oliveiro wrote:

On 21 Apr 2025 08:24:22 +1000, Computer Nerd Kev wrote:
>

It sounds like they're talking about the cache in the drive itself,
making sure data is physically written out before power-off.

>
Unfortunately, you could be right.
>
I say “unfortunately“, because I think it’s a dumb idea for drives
to have
their own cache.

Not at all. There is a huge speed improvement.

 
The key is to have a large enough capacitor in the drive to flush all
those caches on power off.

You still need to protect caches and buffers higher up the stack, or (if
possible) design your system to be resilient against power failure. (For
example, a mail server will only tell an SMTP client that it’s recieved
a message when it’s completed an fsync() on the queue file.)

Storage devices need _some_ internal buffering, to manage the
relationship between the logical blocks visible to the host device and
the physical storage. If that’s too small then a hard disk risks
spending all its time seeking between tracks rather than actually
reading or writing anything (or some differently structured waste of
time on an SSD).

--
https://www.greenend.org.uk/rjk/