Date: Sat, 24 Sep 2005 16:03:10 -0500 From: Colin Farley <Colin.Farley@ecarecenters.com> To: freebsd-stable@freebsd.org Subject: Re: geom_mirror and ggatec/d safe for filesystem replication? Message-ID: <OF9C60EBB9.0097FC06-ON86257086.0073A5C2-86257086.0073A5C7@ecarecenters.com>
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I can't say if this config is safe because I don't have any exper ieince with it. But, I can say that I use rsync to sync filesystems on
two = boxes. They are ftp servers running openbsd using carp for auto
failo= ver. The backup runs a script to sync a portion of it's
filesyst= em with the master after checking to make sure it's still
the backup. = The sync happens every 5 seconds over a Gbit private
network between the t= wo. The data that is being synced is
normally fairly small. = ; Has been working very well in production
for about 9 or 10 months. = You might want to look into rsync as an
alternative if it is practical for = the data you are wanting to
replicate.
Colin
-----owner-freebsd-stable@freebsd.org wrote: --= ---
To:= freebsd-stable@freebsd.org
From: Brian Candler <B.Candler@pobox.com&= gt;
Sent by: owner-freebsd-stable@freebsd.org
Date: 09/24/2005 09:21A= M
Subject: geom_mirror and ggatec/d safe for filesystem
replication?
Consider the following scenario:
- Machine 1 has a UFS filesy= stem on a block device.
- It is mirrored to a block device on machine 2,= using
geom_mirror
and ggatec/ggated
- Machine 2 mounts this = filesystem read only.
My question is: is this last step safe?
When an update occurs on machine 1, certain disk blocks will change
"under the nose" of machine 2's mounts. Will all necessary caches be
invalidat= ed?
(e.g. block caches, inode caches) Or could this result in nasty
beha= viour,
up to and including panics?
If so, is there a safer or bet= ter way of performing real-time
filesystem
replication?
Thanks,
Brian Candler.
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References
1. file://localhost/tmp/3D"ht
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