Multi-machine mirroring choices

[Oliver Fromme]

Sven Willenberger wrote:
 > [...]
 > 1) I have been using ggated/ggatec on a set of 6.2-REL boxes and find
 > that ggated tends to fail after some time leaving me rebuilding the
 > mirror periodically (and gmirror resilvering takes quite some time). Has
 > ggated/ggatec performance and stability improved in 7.0? This
 > combination does work, but it is high maintenance and automating it is a
 > bit painful (in terms of re-establishing the gmirror and rebuilding and
 > making sure the master machine is the one being read from).

First, some problems in ggated/ggatec have been fixed
between 6.2 and 6.3.  Second, you should tune it a little
to improve performance and stability.  The following
reply in an earlier thread is interesting:

http://lists.freebsd.org/pipermail/freebsd-stable/2008-January/039722.html

 > 2) Noting the issues with ggated/ggatec in (1), would a zpool be better
 > at rebuilding the mirror? I understand that it can better determine
 > which drive of the mirror is out of sync than can gmirror so a lot of
 > the "insert" "rebuild" manipulations used with gmirror would not be
 > needed here.

I don't think there's much of a difference between gmirror
and a ZFS mirror if used with ggated/ggatec.  Of course,
ZFS has more advantages, like checksumming, snapshots etc.,
but also the disadvantages that it requires considerably
more memory.

Yet another way would be to use DragoFly's "Hammer" file
system which is part of DragonFly BSD 2.0 which will be
released in a few days.  It supports remote mirroring,
i.e. mirror source and mirror target can run on different
machines.  Of course it is still very new and experimental
(however, ZFS is marked experimental, too), so you probably
don't want to use it on critical production machines.

(YMMV, of course.)

Best regards
   Oliver

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main(){for(;b=c,c-=14;i=printf("%04d",e+d/a),e=d%a)
while(g=--b*2)d=h*b+a*(i?f[b]:a/5),h=d/--g,f[b]=d%g;}