dump(8) using snapshot + "recommended" cache
AHamiltonWright at MtA.ca
Sun Feb 1 12:07:52 PST 2009
On Sun, 1 Feb 2009, RW wrote:
>> ***It is recommended that you always use this option when
>> dumping a snapshot.***
> When you dump a snapshot there are, by definition, no changes between
> passes. So it's saying that in that case there in no reason not to
Ah, that makes sense. That being the case, perhaps we can update
the text to:
If dumping from a snapshot, the filesystem is already frozen,
therefore using a cache with a snapshot will ensure that
consistency is maintained while also providing best performance.
If that sounds good, I'll make a doc patch.
Out of curiosity, under what circumstances is the improved performance
the most likely? I dump from cron when the system usage is low, and
haven't noticed any significant difference in time with or without
cacheing -- but I haven't done any testing under heavy load, nor with
limited RAM, so there are many mbufs available in any case.
Thanks for the info,
More information about the freebsd-questions