On Sun, 3 Nov 2013, [email protected] wrote:
On Fri, Nov 01, 2013 at 01:23:12PM -0600, Warren Block wrote:
On Fri, 1 Nov 2013, [email protected] wrote:
+ Implement new things. Some ideas I have had:
+ GEOM "ERASE" - Rewrite deletes into random writes.
+ GEOM "PLUG" - Persistent version of the connect/disconnect verbs
where the flag sits in the class metadata. This might be a cleaner
approach, rather than adding the verbs to all the existing
providers.
+ GEOM "TAP" - Allow userspace processes to hook into the GEOM
API. Intended for debugging and development.
+ GEOM "WCACHE" - Allow you to use small, fast provider as a buffer
for a larger, slower provider.
+ GEOM DTrace provider. Provide GEOM specific probes to complement
the IO provider.
+ Probably other bits I can't remember right now.
How about an explicit geom retaste command? "true > /dev/ada0" is
misleading to the reader.
Yes, that would be good. It's on my list.
Also, a RAM-cached version of gmirror that would report writes finished
as soon as the faster drive finishes. Kind of the opposite of the
WCACHE above. This would permit creating mirrors of an SSD and hard
drive without performance loss, at least up until available write
buffer space runs out. This one may not be so easy.
I can see the benefit. This would be like a mirror with a journal. As
long as it has a different name from mirror, 'lazy mirror' ?, I think it
would be interesting. The only concern I have would be that some users
could use it and assume the normal mirror semantics, e.g. that all discs
are equally redundant, which wouldn't be true.
I've been calling it a "slow" mirror. Come to think of it, that's a
little misleading. "Async mirror"? There may be an existing term. As
pointed out, it's probably non-trivial to implement. The WCACHE you
suggest above (the Linux guys have "bcache") is probably more benefit to
more people.
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