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Date:      Thu, 18 Sep 1997 18:06:32 -0400
From:      Mark Mayo <mark@quickweb.com>
To:        John Polstra <jdp@polstra.com>
Cc:        Conrad Sabatier <conrads@neosoft.com>, stable@FreeBSD.ORG
Subject:   Re: Error message while cvsup'ing RELENG_2_2
Message-ID:  <19970918180632.16270@vinyl.quickweb.com>
In-Reply-To: <199709182106.OAA09275@austin.polstra.com>; from John Polstra on Thu, Sep 18, 1997 at 02:06:18PM -0700
References:  <XFMail.970916192506.conrads@neosoft.com> <199709182106.OAA09275@austin.polstra.com>

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On Thu, Sep 18, 1997 at 02:06:18PM -0700, John Polstra wrote:
> > >Was the filesystem mounted async at the time of the crash?  I'm
> > >just curious.
> >
> > Um, I'm really not sure what that is, to be honest. :-)
> 
> It is a special option you can use to mount a filesystem.  It makes
> operations on the files and directories substantially faster, but it
> also creates a real risk of losing data (maybe a lot of data) if
> there is a power failure or system crash.  I personally don't
> recommend  using it.

If you're using a UPS, I don't see the risk in using the async option.
>From my own experience, it does make a *dramatic* difference in FS
performance. In the end though, I mount without async on servers since
I'm too afraid of what would happen in a big crash. On my workstation
I use async all the time though - I've experimented with power failures
and async and like you said, you will probably loose any files that were
being written to when the power died. But a power failure while the
system is inactive seems to cause no damage (for example, I leave my
machine on all the time at home, and sometimes there are small power
failures at night). Now that I have a UPS at home, I feel much better
though :-)

Still, every day I think about mounting -async on the servers.. The
server machines I look after aren't terribly busy, and in the 2 years or
so I've been using FreeBSD on them I've never had a system crash. That
combined with the gigantic UPS's that power the machines makes be think
that the chances of something actually going wrong and loosing data on
an async mounted FS is very, very small. Probably more likely that something
would physically go wrong with the machine or HD causing data loss - and
that's what the backup tapes are for!  :-)

cya,
-mark

>    John D. Polstra & Co., Inc.                Seattle, Washington USA
>    "Self-knowledge is always bad news."                 -- John Barth

-- 
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