Re: [ANNOUNCE] Ext3 vs Reiserfs benchmarks

From: Bill Davidsen (davidsen@tmr.com)
Date: Thu Jul 18 2002 - 09:50:34 EST


On Tue, 16 Jul 2002, Andreas Dilger wrote:

> This is all done already for both LVM and EVMS snapshots. The filesystem
> (ext3, reiserfs, XFS, JFS) flushes the outstanding operations and is
> frozen, the snapshot is created, and the filesystem becomes active again.
> It takes a second or less. Then dump will guarantee 100% correct backups
> of the snapshot filesystem. You would have to do a backup on the snapshot
> to guarantee 100% correctness even with tar.

I think I'm missing a part of this, the "a snapshot is created" sounds a
lot like "here a miracle occurs." Where is this snapshot saved? And how do
you take it in one sec regardless of f/s size? Is this one of those
theoretical things which requires two mirrored copies of the f/s so you
will still have RAID-1 after you break one? Or are changes journaled
somewhere until the snapshot is transferred to external media? And how do
you force applications to stop with their files in a valid state?

-- 
bill davidsen <davidsen@tmr.com>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

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