Journaling UFS with gjournal.

[Oliver Fromme]

Pawel Jakub Dawidek <pjd at freebsd.org> wrote:
 > Rong-en Fan wrote:
 > +> I think I must miss something in this announcement. How
 > +> much space will be used for journal? For example, if
 > +> the provider is 80G, how much I will lost due to gjournal?
 > 
 > The size of the journal don't depend on file system size. It more depend
 > on your disk speed and file system load. For example your disk can write
 > at 60MB/s. Journal switch time is 10 seconds. The journal provider has
 > to have place to keep two journals (active and inactive). So bascially
 > you need 60*10*2MB + gjournal headers. I think 2GB is a safe default.

But what happens in the case when you have only one provider?
You wrote that you can specify only one provider (e.g. one
partition) to gjournal, which will be used for both journal
and file system data.  In that case, how do you tell how much
space is used for the journals and how much space is left for
the file system?  It didn't become clear from the examples in
your initial mail.

Another question:  What happens if you (accidentally) make
the journals provider too small, so it hits the end before
the next regular switch?

Best regards
   Oliver

PS:  I've also sent a follow-up to the -fs mailing list a few
days ago, containing a few questions ...  did you overlook it?

PPS:  Thanks again for all your work on journaling!  It
looks very cool and promising.  Any plans to commit it?
A wider audience will speed up the process of polishing
the rough edges, I think.

-- 
Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
Any opinions expressed in this message may be personal to the author
and may not necessarily reflect the opinions of secnetix in any way.

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