Re: Journaling pointless with today's hard disks?

[H. Peter Anvin]

Followup to:  <9tumf0$dvr$[e-mail]>
By author:    "H. Peter Anvin" <[e-mail]>
In newsgroup: linux.dev.kernel
> 
> Indeed; having explicit write barriers would be a very useful feature,
> but the drives MUST default to strict ordering unless reordering (with
> write barriers) have been enabled explicitly by the OS.
> 

On the subject of write barriers... such a setup probably should have
a serial number field for each write barrier command, and a "WAIT FOR
WRITE BARRIER NUMBER #" command -- which will wait until all writes
preceeding the specified write barrier has been committed to stable
storage.  It might also be worthwhile to have the equivalent
nonblocking operation -- QUERY LAST WRITE BARRIER COMMITTED.

	-hpa
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