[ale] Disaster Recovery - HELP!

[Greg]

As far as I know it is impossible because you lose parity when you lose 2,
and it is impossible to know the state of the bits of the missing disks, or
am I totally/partially wrong ??  I thing that what you are seeing is the
remaining information (since parity is shared over the disks, but anymore
in-depth info is missing).  I am going from info from
http://www.acnc.com/04_01_05.html

Of course, if you could recover 1 disk it would be enough to recover the
raid, yes ?

Greg Canter

> -----Original Message-----
> From: ale-admin at ale.org [mailto:ale-admin at ale.org]On Behalf Of Dow Hurst
> Sent: Tuesday, March 25, 2003 11:56 AM
> To: ale at ale.org
> Subject: Re: [ale] Disaster Recovery - HELP!
>
>
> This type situation of a corrupted file system has come up several times
> on the list.  Could we develop a collaborative talk with several experts
> contributing practical ideas on file system recovery as a talk at one of
> the meetings?  Just a suggestion.
>
> I think a dd piped into a tar file to tape or another drive would be in
> order at this point for Jonathon, but this is just what I've learned
> watching Bob do his thing.  Jonathon, take each drive and put them one
> at a time into a box where you have a tape or more disk space.  dd and
> pipe into tar each one of the drives to capture a permanent copy of what
> you have.  Then, after you finish the dd, go back to working on the RAID
> recovery.  You can always use Bob's trick of using grep on a tar file to
> find stuff.
>
> Or, you could just call Bob and let him help you out!
> Dow
>
>
> Danny Cox wrote:
>
> >Jonathan,
> >
> >On Tue, 2003-03-25 at 10:08, Jonathan Glass wrote:
> >
> >
> >>Anyone ever tried to recover data from a hardware RAID 5
> partition after losing
> >>2 out of 5 disks?  The directory structure appears, but I get
> INPUT/OUTPUT
> >>errors when trying to LS directories.  Any thoughts on how to
> recover, except
> >>from tape?
> >>
> >>
> >
> >	One thought: find "raidreconf", now part of the raid tools
> package, I
> >think.  It can "export" from a RAID5 to a single disk.  The RAID must be
> >shutdown/offline, and it runs entirely in user space.  You'll still get
> >errors, but what it can read, it will.
> >
> >	Again, this is just an idea.  It may work, and it may not.... :-(
> >
> >	Caveat: I wrote the RAID5 code, so beware! ;-)
> >
> >
> >
>
> --
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