Fw: Best way for a gmirrored gjournal?

Patrick Hurrelmann outi at bytephobia.de
Mon Oct 29 22:30:36 PDT 2007

Dear all,

I'm forwarding this message to this lists, as current@ obviously was
the wrong recipient.

I kindly ask you for your ideas and proposals on my questions below.


Begin forwarded message:

Date: Mon, 22 Oct 2007 19:08:35 +0200
From: Patrick Hurrelmann <outi at bytephobia.de>
To: freebsd-current at freebsd.org
Subject: Best way for a gmirrored gjournal?

Hi all,

Currently I'm trying to install a new server and need some hints on how
to best configure filesystems using gmirror and gjournal.

The server in question is a amd64 with 512mb of ram and 2x 80gb sata
hdds. So I was thinking of a mount-point layout like the following:

 /       (1gb)
 swap    (1gb)
 /var    (8gb)
 /tmp    (1gb)
 /home   (4gb)
 /usr   (13gb)
 /jails (39gb)
 10gb for journaling

Which would leave a space of 10gb for journaling. I digged through the
mailinglist-archives and man-pages of gmirror and gjournal but all I
ended up with are questions and doubts :)

Now I wanted to create 2 mirrors (gm0s1 and gm0s2). Gmirror gm0s1
containing the slices ad0s1 and ad2s1, while gm0s2 should contain ad0s2
and ad2s2. I created 2 slices, as with the above shown partitioning I
was running out of mount-points for this slice.

Is such a layout reasonable? Or is it stupid to use a dedicated slice
just for journaling and better skip e.g /tmp partition to leave space
for a dedicated journaling partition on this slice? Btw. are 10gb
enough for journaling of 6 partitions? Or do I need one dedicated
partition for journaling each?

If I skip using a separate partition for journaling data, gjournal keeps
telling me that e.g. the root partion of 1gb is too small for
jorunaling. Would it be save to decrease journal size altough man-page

What do you people out there suggest? How do you handle systems with
gmirror and gjournal combined? Or even use ZFS although ram is limited
(as the machine will serve up several jails with e.g. postgres)? 

I'm really looking forward to suggestions from you. I intentionally
directed this mail to current@ as I think that here are the most people
around with experience on gjournal. But if I better should direct this
mail to questions@ I'm happy to do so, too.

Best regards,


Patrick Hurrelmann   | "Programming today is a race between software
Mannheim, Germany    | engineers striving to build bigger and better
                     | idiot-proof programs, and the Universe trying
outi at bytephobia.de   | to produce bigger and better idiots. So far,
www.bytephobia.de    | the Universe is winning."         - Rich Cook

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