Re: power failure causes files loss - Hans-Peter Jansen

From: "Hans-Peter Jansen" <hpj@urpla.net>
To: xfs@oss.sgi.com
Cc: adamantzj <tzj1983@163.com>, Stan Hoeppner <stan@hardwarefreak.com>
Subject: Re: power failure causes files loss
Date: Sat, 24 Apr 2010 19:05:43 +0200	[thread overview]
Message-ID: <201004241905.44282.hpj@urpla.net> (raw)
In-Reply-To: <4BD21E65.80203@hardwarefreak.com>

On Saturday 24 April 2010, 00:25:41 Stan Hoeppner wrote:
> adamantzj put forth on 4/23/2010 6:28 AM:
> > Hello,
> >
> >      I’m writing data on a server in my company, but power cut
> > suddenly. I had to restart the machine, then I found that many files in
> > the working directory had been lost. I made some tries with xfs_repair
> > and it didn't repair my corrupted file.
> >
> > What are the reasons caused this problem? I would like to know is what
> > can I do to resolve this problem? Is XFS able to recover my file with
> > its right content, at least a consistent content?
> >
> >      I'm running a 2.6.24 kernel with xfsprogs-3.1.1, and the operating
> > system is RedHat Enterprise Linux 5 Server (64-bit).
> >
> >      Do you know if this problem has often been encountered, there is a
> > way to proceed?
> >
> > Thank you !
> >
> > Adamant
>
> XFS isn't the cause of your problem.  Running without a proper UPS is the
> cause of your problem.  Fix the cause of your problem by purchasing a
> properly sized and instrumented/monitored UPS.  YOU CANNOT rely on your
> OS or filesystem driver to prevent data loss due to power loss, or to
> properly recover from such unexpected power loss if/when it occurs.  This
> is why you absolutely need to eliminate the possibility of unexpected
> power loss.  This is the sole purpose for the existence of companies such
> as APC, Liebert, TrippLite and others.
>
> I'd have thought by 2010 that the entire IT cadre worldwide would already
> be educated on proper power backup planning and procedures.  I guess not.
>
> Acquire a proper UPS and configure it properly, specifically meaning
> monitoring and alerts which will allow for performing a proper shutdown
> during an extended outage, and your problems will disappear.

While you're right for the general case of course, there are many other 
failure conditions, that an UPS will not prevent, eg. kernel crashes. 
Therefore there is an vivid interest, that any storage based filesystems  
should stay consistent _any_ time (and usually filesystem developers spend 
an considerable amount of their time on fixing such problems, if they 
arise). 

Adamant, the people reading here are rarely trained in telepathic   
capabilities. If you need more specific answers, you need to provide more 
specific details, eg. mount options, error logs, etc.

Pete

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