Subject: Re: fsck and soft updates (soft dependencies)
To: NetBSD Users's Discussion List <>
From: Greg A. Woods <>
List: netbsd-users
Date: 09/04/2006 23:53:06
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At Tue, 22 Aug 2006 14:30:16 -0700,
Chuck Swiger wrote:
> For the most part, filesystem snapshots have worked pretty well under =20
> a bunch of cases on FreeBSD; the example of using dump/restore is a =20
> good one, also for trying to obtain a more consistent file-level =20
> backup of an active database, and so forth.

Unless you've done something to integrate some kind of consistency
flush/halt feature into your database software there's no guarantee of a
consistent file or file-system level backup of any active database,
especially not if you're talking about anything more sophisticated than
a flat text files maintained with awk and join et al.  You must still
stop your database completely to ensure that any data still cached in in
any process is flushed and the file-level data is 100% consistent.  Of
course with using filesystem snapshots the database downtime that is
necessary is far shorter than without that feature -- almost
unnoticeable for many types of DB applications.

						Greg A. Woods

H:+1 416 218-0098 W:+1 416 489-5852 x122 VE3TCP RoboHack <>
Planix, Inc. <>       Secrets of the Weird <>

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